As of now, there will only ever be 21 million bitcions in circulation.
I'm told that this is usually an inconsequential fact, due to the fact that bitcoins can be subdivided into 8 decimal places (and these can be expanded in the future if needed)
But, is that really the most convenient of routes?
In the far future, lost coins may add up to a very big problem. Currently, I know of no way in which a truly lost coin can be returned to the market. Imagine someone with thousands of BTC in their wallet for instance, if their computer crashes, or they die, or forget their password, or they accidentally send the BTC to the wrong address, their bitcoins can become unrecoverable. Implicitly, this increases the value of all the others because now there are BTC that can never be spent, but it's difficult to track this.
So what happens decades from now, when a truly significant number of coins are lost?
Does the system ever have a sense for how old coins really are? Is it a good idea to find them and re-introduce them back into circulation after an appropriate time? Or are we faced with an ever-dwindling supply of coins?
Search before you ask, this question has been asked repeatedly, repeatedly, repeatedly, repeatedly, and repeatedly