Unexpected discovery. Assuming total hyperbitcoinization does occur, even once the block subsidy hits zero, the "break-even" cost to maintain the current all-time high network security in sats/vbyte terms is under 1 sat/vbyte. That assumes no improvements in electrical efficiency too. So even if nearly all of the transactions are occurring off-chain, the few that do need to use onchain can keep the network secure rather easily for hundreds if not thousands of years.