Idk, I've seen plenty of books be popular something like 5 years after release, so having those be duplicated by bigger publishers in that time seems like a really bad idea, especially for smaller authors who have a harder time breaking through.
I think 10-15 w/ a one-time renewal for another 10-15 with proof that the rights holder didn't recoup their investment sounds reasonable. They'd have to pay for that renewal (probably relative to expected/past sales), but it would be an option. It would suck to be at year 10 after launch, and suddenly there's a ton of demand for your book (say, your recent release broke through, and people are reading your older works) so a different publisher swoops in and steals all of that profit. Or maybe a big movie producer decides to make a movie based on your book about 10 years after it has released, should they be allowed to just not pay you for that work?
The copyright system certainly has problems, but it does provide value to smaller creators.