Either there remains interest and social consensus around this ledger, in which case it can be rebooted on a different network, for example, or even by a centralized party; or maybe you are the only one with an interest in your NFT collection, in which case you can keep a copy of the ledger yourself.

I'm not convinced. Art galleries are easy to launch, even in 500 years time. What you're describing is hard to do.

I can fork a centralized copy of a chain much more easily than I can start a gallery.

Sure you can do that right now. But my point was more: physical objects can be traded easily in the far future.

We can hardly rebuild stuff from source after 20years time, so I'm pretty sure you will not be able to revive long dead blockchains as easy as renting a space to trade physical objects of collectible value.

My point here was more akin to saying: Sure, if no one cares about your NFT, or the chain it is on, then yes, it's worthless. If you want to be the last one to care, keep a copy of the chain.

The physical equivalent is a worthless painting that no one cares about and your grandchildren throw out.