user116324: As the reward is lower, less effort is spend in mining new bitcoins. How the transactions fees will evolve would be quite crucial the get the miners activity down (and their energy consumption). I would assume that the transactions fees would stay at very low levels, because every miner has always an incentive to add any transaction with a positive fee.
Additional question: For sure there are some cryptocurrencies which reached that state (of no mining new coins). How did the transaction fees evolve after mining the last coin?

user116353: What this means is that going forward the cost of securing currency will keep increasing and it will be difficult to transact in smaller denominations, it will turn into asset that just can not be transacted at smaller sizes, will not really be a payment instrument.
I think to keep security but allow for higher transactions by increasing block size to allow significantly large transactions, possibly 65K per block, should make it viable for longer term.
Right now it is very difficult to confirm small transaction unless fee is more than transaction value.

user24925: 
I would assume that the transactions fees would stay or converge to be very low levels, because every miner has always an incentive to add any transaction with a positive fee.

Block space is finite, so users are bidding for their position within the next block. Miners will always choose the transactions which have the highest feerate because it makes their income the highest. Today the fee rate often makes up a significant ($100k+ USD) portion of the total block reward.

https://mempool.space/

How the transactions fees will evolve would be quite crucial the get the miners activity down (and their energy consumption).

Mining activity would reduce naturally if there was less reward, but there's no opportunity for changing core principles of Bitcoin like this.
As a valuable currency Bitcoin needs to be predictable and justifiable, if the rules dramatically changed it would make a fairly lousy currency. You wouldn't be able to invest in mining hardware for example, if you couldn't model even the base income a couple of months into the future. Making even small changes to the economics of the system opens the floodgates for others. ultimately.

For sure there are some cryptocurrencies which reached that state (of no mining new coins). How did the transaction fees evolve after mining the last coin?

There's no useful comparisons to be made, nothing has the scale, maturity, and properties of Bitcoin.

116324: <p>As the reward is lower, less effort is spend in mining new bitcoins. How the transactions fees will evolve would be quite crucial the get the miners activity down (and their energy consumption). I would assume that the transactions fees would stay at very low levels, because every miner has always an incentive to add any transaction with a positive fee.</p>
<p>Additional question: For sure there are some cryptocurrencies which reached that state (of no mining new coins). How did the transaction fees evolve after mining the last coin?</p>
 116353: <p>What this means is that going forward the cost of securing currency will keep increasing and it will be difficult to transact in smaller denominations, it will turn into asset that just can not be transacted at smaller sizes, will not really be a payment instrument.
I think to keep security but allow for higher transactions by increasing block size to allow significantly large transactions, possibly 65K per block, should make it viable for longer term.
Right now it is very difficult to confirm small transaction unless fee is more than transaction value.</p>
 24925: <blockquote>
<p>I would assume that the transactions fees would stay or converge to be very low levels, because every miner has always an incentive to add any transaction with a positive fee.</p>
</blockquote>
<p>Block space is finite, so users are bidding for their position within the next block. Miners will always choose the transactions which have the highest feerate because it makes their income the highest. Today the fee rate often makes up a significant ($100k+ USD) portion of the total block reward.</p>
<p><a href="https://i.stack.imgur.com/jaz6a.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jaz6a.png" alt="enter image description here" /></a></p>
<p><a href="https://mempool.space/" rel="nofollow noreferrer">https://mempool.space/</a></p>
<blockquote>
<p>How the transactions fees will evolve would be quite crucial the get the miners activity down (and their energy consumption).</p>
</blockquote>
<p>Mining activity would reduce naturally if there was less reward, but there's no opportunity for changing core principles of Bitcoin like this.</p>
<p>As a valuable currency Bitcoin needs to be predictable and justifiable, if the rules dramatically changed it would make a fairly lousy currency. You wouldn't be able to invest in mining hardware for example, if you couldn't model even the base income a couple of months into the future. Making even small changes to the economics of the system opens the floodgates for others. ultimately.</p>
<blockquote>
<p>For sure there are some cryptocurrencies which reached that state (of no mining new coins). How did the transaction fees evolve after mining the last coin?</p>
</blockquote>
<p>There's no useful comparisons to be made, nothing has the scale, maturity, and properties of Bitcoin.</p>
