user11674: The Buddha put high emphasize on Anicca and thus it shouldn't be dismissed. Now my question: When should one remind oneself of the transience of all phenomena? I doubt in every occassion. 
If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking. So this then is a rather concentration excercise without pañña (wisdom), right?

user295: The transient nature of all experiences (pleasant, unpleasant, neutral) is the forerunner of unsatisfactoriness.
So when doing your daily chores look what sensations associated with it. A certain posure may be comfortable, uncomfortable or neutral. When you are walking also there are many little sensations throughout the body. If you are walking barefoot on gravel it might be painful. If you have been seated and you legs are numb then walking may be plesent. Likes whise see how the sensations change. This is this is also the link to the 1st Noble Truth, Causality and Dependent Origination. This is further elaborated in this answer.

user-1: 
When should one remind oneself of the transience of all phenomena?

24 hours a day. Ideally. Until that becomes possible, practice as frequent as possible, while working on balancing the five spiritual faculties. Reminding is not enough - it should be insight meditation (vipassana) which is practiced. Intellectually reminding oneself, will lead not to insights.

If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking. So this then is a rather concentration excercise without pañña (wisdom), right?

Depends on what kind of meditation practice you are doing. To gain insights into the impermanent nature of phenomena, one should practice insight meditation.
Walking meditation is very beneficial and its a great vehicle to carry over your sitting practice into daily life.
By doing a "moving" meditation it will also become easier for you to remain mindful throughout your day, while doing daily activities, such as taking a shower, brushing your teeth, doing the dishes.
Here are 2 videos on walking meditation by Ven. Yuttadhammo:

How To Meditate III - Walking Meditation
Ask A Monk: Why Walking Meditation Comes First

Also here is an article on "The Benefits of Walking Meditation" by Sayadaw U Silananda.

user8157: 
The Buddha put high emphasize on Anicca and thus it shouldn't be dismissed.

The Buddha put an emphasis on many dhammas. 
The Buddha did not actually teach to constantly remind oneself of anicca because this would mean the mind is always thinking. Instead, one only reminds oneself of anicca when necessary.
The goal of meditation is to stop thinking so the mind has concentration so it can develop calm and then see anicca directly (rather than reminding oneself about anicca).
Reminding oneself about 'anicca' is called 'anicca sanna'. Where as seeing anicca directly is called 'vipassana'. Reminding oneself about 'anicca' is not 'vipassana' 

Now my question: When should one remind oneself of the transience of all phenomena? I doubt in every occasion.

'Reminding oneself' is called 'mindfulness'. 
The wisdom (panna) used with reminding oneself is called 'sampajanna' ('situational wisdom'). 
'Reminding onself about impermanence' is called 'anicca sanna'. 
'Anicca sanna' is a preliminary practice (mentioned in MN 62 & MN 118) & particularly useful when there is a very strong hindrance that one cannot control and thus must endured; patiently waiting for the energy of the hindrance to dissipate & dissolve. 
It is also done whenever necessary when something must be endured or when something is lost. Such as when you dislike a poster on the internet or lose a debate on the internet. You can think: "This internet is impermanent; this debate is impermanence". 
For example, you have a good meditation, which then ceases, due to hindrances. If the mind clings to the good meditation wishing to have it all the time, one can reflect on impermanence to get rid of the craving. 
Or if your mother nags you to do your chores, you reflect: "This nagging is impermanent; the sound is impermanent; doing the chores is impermanent". 

If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking.

No. The purpose of sati is not to remember you are walking. The purpose of sati is to remember to walk with wisdom or to do chores with wisdom.
For example, in a monastery, everyone must do chores. The chores are done with the wisdom that defilements lead to suffering therefore to do chores without defilements. 

So this then is a rather concentration excercise without pañña (wisdom), right?

Sati is never without wisdom. Sati always has sampajanna. Sati is only remembering or calling something to mind. Mindfulness must remember to apply wisdom. Therefore, mindfulness & wisdom always operate together. There cannot be mindfulness without wisdom. This is why the term 'sati-sampajanna' is often used, as a compound.
Why would we walk or do chores without wisdom? If we do not have any wisdom about the purpose of walking meditation or doing chores & how to do it, why would we do it? For what purpose? With what method? For what benefit? 
This video might help: Buddhist Meditation Sati Sampajanna
This book might help: Part II. The Use of Dhamma

11674: <p>The Buddha put high emphasize on Anicca and thus it shouldn't be dismissed. Now my question: When should one remind oneself of the transience of all phenomena? I doubt in every occassion. </p>

<p>If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking. So this then is a rather concentration excercise without pañña (wisdom), right?</p>
 295: <p>The transient nature of all experiences (pleasant, unpleasant, neutral) is the forerunner of unsatisfactoriness.</p>

<p>So when doing your daily chores look what sensations associated with it. A certain posure may be comfortable, uncomfortable or neutral. When you are walking also there are many little sensations throughout the body. If you are walking barefoot on gravel it might be painful. If you have been seated and you legs are numb then walking may be plesent. Likes whise see how the sensations change. This is this is also the link to the 1st Noble Truth, Causality and Dependent Origination. This is further elaborated in <a href="https://buddhism.stackexchange.com/a/21545/295">this answer</a>.</p>
 -1: <blockquote>
  <p>When should one remind oneself of the transience of all phenomena?</p>
</blockquote>

<p>24 hours a day. Ideally. Until that becomes possible, practice as frequent as possible, while working on balancing the five spiritual faculties. Reminding is not enough - it should be insight meditation (vipassana) which is practiced. Intellectually reminding oneself, will lead not to insights.</p>

<blockquote>
  <p>If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking. So this then is a rather concentration excercise without pañña (wisdom), right?</p>
</blockquote>

<p>Depends on what kind of meditation practice you are doing. To gain insights into the impermanent nature of phenomena, one should practice insight meditation.</p>

<p>Walking meditation is very beneficial and its a great vehicle to carry over your sitting practice into daily life.</p>

<p>By doing a "moving" meditation it will also become easier for you to remain mindful throughout your day, while doing daily activities, such as taking a shower, brushing your teeth, doing the dishes.</p>

<p>Here are 2 videos on walking meditation by Ven. Yuttadhammo:</p>

<ul>
<li><a href="https://www.youtube.com/watch?v=_IFvablc6EI" rel="nofollow noreferrer"><em>How To Meditate III - Walking Meditation</em></a></li>
<li><a href="https://www.youtube.com/watch?v=aucEZdM9DKE" rel="nofollow noreferrer"><em>Ask A Monk: Why Walking Meditation Comes First</em></a></li>
</ul>

<p>Also here is an article on <a href="http://www.accesstoinsight.org/lib/authors/silananda/bl137.html" rel="nofollow noreferrer"><em>"The Benefits of Walking Meditation"</em></a> by Sayadaw U Silananda.</p>
 8157: <blockquote>
  <p><strong>The Buddha put high emphasize on Anicca and thus it shouldn't be dismissed.</strong></p>
</blockquote>

<p>The Buddha put an emphasis on many dhammas. </p>

<p>The Buddha did not actually teach to constantly remind oneself of anicca because this would mean the mind is always thinking. Instead, one only reminds oneself of anicca when necessary.</p>

<p>The goal of meditation is to stop thinking so the mind has concentration so it can develop calm and then see anicca directly (rather than reminding oneself about anicca).</p>

<p>Reminding oneself about 'anicca' is called 'anicca sanna'. Where as seeing anicca directly is called 'vipassana'. Reminding oneself about 'anicca' is not 'vipassana' </p>

<blockquote>
  <p><strong>Now my question: When should one remind oneself of the transience of all phenomena? I doubt in every occasion.</strong></p>
</blockquote>

<p>'Reminding oneself' is called 'mindfulness'. </p>

<p>The wisdom (panna) used with reminding oneself is called 'sampajanna' ('situational wisdom'). </p>

<p>'Reminding onself about impermanence' is called '<em>anicca sanna</em>'. </p>

<p>'Anicca sanna' is a preliminary practice (mentioned in MN 62 &amp; MN 118) &amp; particularly useful when there is a very strong hindrance that one cannot control and thus must endured; patiently waiting for the energy of the hindrance to dissipate &amp; dissolve. </p>

<p>It is also done whenever necessary when something must be endured or when something is lost. Such as when you dislike a poster on the internet or lose a debate on the internet. You can think: "<em>This internet is impermanent; this debate is impermanence</em>". </p>

<p>For example, you have a good meditation, which then ceases, due to hindrances. If the mind clings to the good meditation wishing to have it all the time, one can reflect on impermanence to get rid of the craving. </p>

<p>Or if your mother nags you to do your chores, you reflect: "<em>This nagging is impermanent; the sound is impermanent; doing the chores is impermanent</em>". </p>

<blockquote>
  <p><strong>If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking.</strong></p>
</blockquote>

<p>No. The purpose of sati is not to remember you are walking. The purpose of sati is to remember to walk with wisdom or to do chores with wisdom.</p>

<p>For example, in a monastery, everyone must do chores. The chores are done with the wisdom that defilements lead to suffering therefore to do chores without defilements. </p>

<blockquote>
  <p><strong>So this then is a rather concentration excercise without pañña (wisdom), right?</strong></p>
</blockquote>

<p>Sati is never without wisdom. Sati always has sampajanna. Sati is only remembering or calling something to mind. Mindfulness must remember to apply wisdom. Therefore, mindfulness &amp; wisdom always operate together. There cannot be mindfulness without wisdom. This is why the term 'sati-sampajanna' is often used, as a compound.</p>

<p>Why would we walk or do chores without wisdom? If we do not have any wisdom about the purpose of walking meditation or doing chores &amp; how to do it, why would we do it? For what purpose? With what method? For what benefit? </p>

<p>This video might help: <a href="https://www.youtube.com/watch?v=rpCy9Tb73gw&amp;t=7s" rel="nofollow noreferrer">Buddhist Meditation Sati Sampajanna</a></p>

<p>This book might help: <a href="http://www.dhammatalks.net/Books/Bhikkhu_Buddhadasa_Natural_Cure_for_Spiritual_Disease2.htm" rel="nofollow noreferrer">Part II. The Use of Dhamma</a></p>
