There's no defined stop point for physical development either... Top performing athletes still have trainers, and nobody sees that as a problem. If it's mental development though, it must have a stop point?
There is nothing stopping them from exiting therapy. The therapist may be aware that the person is still a basket case but if they are non-violent they are free to roam.
It's not at all. There are plenty of stories of people who realized that therapy was just causing them to ruminate on their problems, and that the therapist was just milking them for years before they wised up and walked away. That's not what I call "obvious".
This is precisely why I stopped going.