the ultimate, primary intended beneficiary is the public

even with extrememly long lifetimes, having to renew copyright every decade or two (with some noticable but not giant registration fee) will be more of a bother than it's worth for the vast majority of works, even while the author is alive.

In any case where the lifetime of the 'next generation' is a problem, the lifetime of the author will be a problem shortly afterwords (with the next generation of authors). So it's not a problem I think we have to specifically address now.