I have hypothyroidism. My thyroid meds have been stable for a long time now. Psych meds have not. They are changing quite frequently, but I really don't think it, or my major episodes are caused by my thyroid issues.

How long you can expect stability would all depend on your meds, how your body reacts to them, and what kind of stresses you are under and how that affects you. Nobody, no matter what med they are on can really say, ok, this med is going to last, or not last because everyone is different and things can change quickly