How much more work should I put to my master's thesis? I have been doing my master's thesis for a year now. I was quite productive during the past months, so I already managed to publish one paper on the topic. 
Now, the productivity seems to have drawbacks too - I have already fulfilled every requirement there is for a thesis, and even more, but I haven't described even half of the work I did during the past year.

So, I am now left wondering should I return the thesis tomorrow for evaluation, or use two or three more months writing (I'm a terribly slow writer). I would probably like to apply for a PhD position, so I guess I should make the decision from that point of view. If I have a very comprehensive master's thesis, does it add any value for application? Having the one paper would already opens all doors in my home country, but I don't know about the others.
Having a paper published on your own work, while doing a Master's degree (i.e. in a relatively short time) sure is a good point of your application to any graduate program. Having a paper submitted for publication is always a plus, but having one already published is a strong plus for you.

Regarding your thesis: the quality of the thesis itself will probably not matter much in admission to a PhD program, unless it is visibly bad, in which case it will sure hurt. Otherwise, chances are noöne will read it through when you apply. Thus, if you are strongly confident that your thesis can be accepted/graded/defended (I don't know what the detailed requirements are for your program) in its current state, don't overdo it.

Don't get me wrong: you don't want to be seen as the guy who did the absolute bare minimum to get away with it. That looks bad, and may leave a stain when people ask for references. Otherwise, if you think your thesis is of good quality, just submit it. The extra work it requires to get it to “perfect” or “awesome” is probably not worth it. The only exceptions I can see are:


if your Master's program has a ranking system, and getting a good rank (or even 1st) can boost your future applications
if the writing will also be useful for new papers, in which case you might as well include it in the thesis