On an exponential curve, even companies would be thinking hard about renewal a few doublings into the process. Even Disney would start getting to the point where they'd be picking and choosing and not just forking over $(2^n × number of works) every year.

Also, I often advocate this, and to some extent I consider it a strategic retreat. Fine. You're a big company and you want to own your stuff forever. But behind the laws protecting those companies there's a ton of stuff that the owner doesn't care, nobody even knows who the owner is, etc. etc. (There's a lot of stuff that is de facto in the public domain because nobody owns it anymore in any practical sense, but there's no way to be sure what that stuff is, and the risk is too large to take.) The stuff the big companies are defending is just a small fraction of what exists. If we tuned the laws to give the big companies what they want (more or less) but stopped protecting everything else it'd be a win. And they can pay an increasingly steep fee for the benefit.

Or, to put it more prosaically, I don't really care how long Steamboat Willy stays under Disney's copyright, I'd like Steamboat Willy to stop shielding everything produced ever.