I’ve said it many times: I think that copyright for all published art should extend for exactly one year after it’s publication then become public domain. For almost ALL media, the first year is the time in which it make over 90% of its money. If you haven’t turned a profit, or at least broken even, by then then you aren’t going to.
After tjay I don’t see why you should be entitles to royalties from every sale, especially with our modern system of mass distribution.