Whereas book characters from long dead authors are a whole different matter. While I think estates should be able to protect the rights of the estate for a period of time the fact that no new content can be created by the author should discount extending the protection. Now interesting cases do arise where direct descendant or designated authors do keep stories and characters progressing, Dune and Pern come to mind.
So where the association is very strong with an active entitle I say let them keep it, where there are degrees of separation, like book examples, then perhaps one generation?