Hi Cy,
Ideally, you would have started out with a higher starting dose, for instance 20-30 mg methimazole or 200-300 mg PTU.
As soon as FT4 fell into range, regardless of the TSH level, your dose should have been lowered to what's called a maintenance dose. This is usually 2.5-10 mg daily for methimazole and 25-150 mg daily for PTU.
Gradually, over time the dose would be lowered based on your FT4 level. You want to make sure your FT4 is at least at mid-range and preferably closer to the high end of the range depending on your symptoms.
If your FT4 is at mid-range, for instance, and you're noticing symptoms of hypothyroidism, your levels could be, while normal, too low for your body's needs. In this case, your ATD dose would need to be lowered a bit raising it closer to the high end of the range. It's a good idea to have regular FT4 for monitoring your meds along with a TSH every now and then as it can quickly predict a move into overt hypothyroidism and it can help predict remission.
If FT3 was elevated at the time of diagnosis then you'd want FT3 levels as well at least until they're back within range. In general, it takes longer for FT3 than FT4 to fall. But since we have so much more FT4 than FT3 dosing is usually based on the FT4 level.
You want a doctor with experience using meds who's willing to work with you. This could be an endocrinologist, family practice doctor, internist, naturopath, or osteopath. A doctor who you can communicate with means more than his or her title.
If you're on a maintenance dose and your labs are stable, you could have follow-up appointments every 2-3 months. But if you were to notice any changes in symptoms you'd want to schedule an appointment sooner.
Best, Elaine