Authors who should have quite while ahead

[Draken]

Have any of you any thoughts on authors who started off well but who you wish had stopped writing sooner than they did?

For me three that spring to mind are:

Isaac Asimov - the cleverness of his early robot stories and the unique vision of the original Foundation trilogy eventually spoiled by increasingly pedantic efforts to weld them all together.

Frank Herbert - ok Dune was initially meant as a trilogy, but the latter two books in it paled in comparison to the brilliant first book. And the ones that followed went downhill fast.

Robert Heinlein - the energy of his "future history" stories, the imagination of "Stranger in a Strange Land" - if you like these, don't read his last few books.

Anyone agree/disagree, or have some nominations of their own?