Transactions are validated by the Bitcoin node network. Bitcoin mining provides a 10-minute delay between blocks to allow nodes to stay synchronized. Bitcoin miners do not need to be paid. Bitcoin mining continues forever

That will be a year 2140 problem

That’s over 100 years from now but love where your heads at

“Users will generate blocks for transaction fees alone.” -Satoshi (probably)

The average transaction fee per block today is 0.1 BTC which is similar to what the block subsidy in a few more halvings.

Miners will earn from fees instead of new supply