I've had this for over 20 years, and only recently received a letter from my GP stating that I am overdue a blood test for my thyroid function. (Yes, about 20 years worth)
Then she went on to say it is very important that this is done on an annual basis. Ha! Doctors - you just gotta love them! Glad I'm still functioning and was utterly clueless (through no fault of mine) that this should be done on a yearly basis.