I am 8 years post thymectomy and have been symptom and medication free since one month after surgery. My symptoms were only ocular, and mestinon did not alleviate symptoms at all.
It is my understanding that unless we test negative for MG, we are to follow the medication contraindications cautions for the rest of our lives. I, for one, will adhere to the cautions strictly to hopefully never show symptoms again.
I am on daily medications that are contraindicated, but only as a matter of necessity (cardiac meds).
Myasthenia Gravis is one of few diseases that has so many drug contraindications. But the cautions are there because so many drugs CAN cause complications.

Lisa