Wouldn’t it be easier to use a simpler mathematical formula? First renewal is fee^2. Second is fee^3, etc. Balance the fee and the term, but eventually you’ll hit a point where the renewal fee is a trillion dollars. If Disney wants to pay off the national debt to keep copyright on “Steamboat Willy” I’m not going to complain.

That avoids the income reporting aspect and allows people to make straightforward time-based predictions on when something enters the public domain.