I had a thymoma also and had surgery in December 2009. Removal is no guarantee of remission. From everything I've read, sometimes people see some improvement within weeks, months, or may be even more than a year. And some folks see no improvement.

At one point I was on both Prednisone and Mestinon. Currently I am on Mestinon 60mg three times a day. It keeps my symptoms at bay and I am leading a pretty normal life. I have double vision flare ups every once in a while (last time was when I was dealing with the stress of my father's death).

You shouldn't mess with your Mestinon dosage without your doctor's approval. Too much can be as bad as too little in some instances.

Hoping things improve for you over the coming months.