If "the right medication(s)" pertain to just bipolar disorder and exclude side effects and other psych issues, my answer is perhaps four years, though I had been on other medication mixes that showed great promise.

As for my best medication mix (it's always been more than one medication) in most respects (bipolar stabilization and mildest side effects) my answer is 11 years.

I'm still disabled. Given this, some may say I've never found the "right medications", but I wouldn't agree with that. What is most disabling to me now are the still open wounds of trauma from my illness experience, and the thin-skinned susceptibility I still have because of them. There is no medication(s) in pill form to ease those. That "medication" is to be found via continued therapy, additional mental healing, and endurance training, of a sort.