I think 5 years is too short. It assumes the creation[tm] will work out of the box and get immediate momentum. Whereas for music and literature it may well take a decade before the thing bubbles up to someone's consciousness.
I'd say 20-25 years from first publication would be a good time window. If your creation has not become worth anything in that time, it wasn't timely or of real interest. On the other hand, if a creation[tm] does become part of cultural background, 25 years is more than enough to reap the benefits. And at the end of the term, if something is part of the cultural scenery, it needs to be in public domain no matter what.
What a window like that would ensure is that creators can earn royalties over time, but it would prevent the inter-generational rent seeking dynasties. Copyright is supposed to encourage creation, by handing over a strictly temporary monopoly, but also guaranteeing that the monopoly remains short enough to enable culture to evolve.
