Old stuff people still care about tends to be good stuff.

If you're still talking about it and it's old it's Lindy.

By default we forget about things as they recede into the distance.

If someone keeps it alive, keeps on pulling it to the present because they find it useful, that's a great sign it matters.

If it's been pulled into the future from a very long time in the past, that's an incredibly strong signal that it's valuable and interesting.