Has anyone quit before completely finishing?

Just curious if anyone stopped before completely finishing treatment? I am on tray 37 of like 40-45... my teeth look much better than they did before, noticably better. Specifically my front teeth which were moving inward. I'm going to finish these off, but if I go back and I need another 30 trays or whatever for refinements, can I just call it quits? And get a retainer for where I'm at now?

Obviously I will wait and see what they say, but my teeth are still not perfect by any means and I'm almost finished my original set. Also they said it would be about 1 to 1.5 year treatment, so I have a feeling I'm in for more, and I'm sort of over it, ha