What's a "sane" point at which you become entitled to other people's work?

What a strange way to phrase it, considering in your last comment you were talking about how copyright expiry is exactly for this purpose.

Anyway, what is copyright expiration in America these days? 100 years?

Also, is it simply a matter of X years after creation? I somehow doubt it's that simple anymore. I wouldn't be surprised if "copyright is extended indefinitely if the work is being actively commercially used" or some such

Patents are for 15-20 years.

Which is saner eh! That way people living at the time who are protecting it (copyright and patents are both protections for things otherwise being distributed and which could be copied easily) can benefit from it eventually.

100 years is just rent extraction.