Well, that’s the question now, isn’t it? And as with all things, it’s all a matter of opinion, really. But just because something sells well doesn’t mean that it couldn’t sell better, or that whatever made it excellent at first has grown stale over time, or a million other things.
I don’t tend to think we have a real problem with having kept creators on books for too long in general, but I can see where other people might feel that way in certain instances.