How long does this bitcoin exist?

• even if only 2 people mine it and trade privately it will continue forever. however the new coin production ends in the year 2140 and the miners then continue mining and getting paid in fee's by anyone that transacts with it.  

•  right now there are ~5million specialised machines mining it which cost money to do that activity. the costs of such are around the $6k figure per coin reward for such activity. which is the underlying base VALUE of it. the bitcoin PRICE is the more fluid thing you see above VALUE which is what people speculate they want to profit over. 

•   from 2009 and up until the year 2140 the coin reward halves every 4 years. and the difficulty to mine it adjusts every two weeks, which is where underlying the volatile price you can calculate a slow increasing underlying base value.

•    as long as people continue to see bitcoin as useful and valuable people will continue mining it and using it. and the value will continue moving. but if people see it as not useful and stop mining it the the underlying value can go down.

•     its not a worry of how long it will last. its about how useful it is and valuable. (i dont just mean the top price i mean the underlying value that supports the top price) 

the post from : https://bitcointalk.org/index.php?topic=5037125.0