Books do not biodegrade in a timeline we'll ever see in our lives unless there's water damage. Which is relatively rare.
It is very much not uncommon to see books several decades old in libraries. And I suppose it is survivorship bias in the most literal sense, but that's because there's so many survivors. It's practically the rule.
Don't they ? I have books printed in the last half of the 20th century where I'm starting to get worried about the yellowing of the pages (and the seemingly degrading structural integrity of the pages).
I've heard it was something about acidic paper (with it also being a plague of cheap printing, while being much less of an issue of expensive printing techniques).
(«several decades old» is a low bar...)