I have a good friend who was off symptom-free and off meds for 10 years. Then she had a full-blown manic episode, won't go into details since it's her story, but she's still trying to put the pieces back together. In retrospect I think she was depressed for the last couple of years.

All my treatment providers have told me it is possible to have long stretches with no symptoms.

Re your last question, all I can say is try to enjoy every day that you are healthy. I'm guessing the longer you feel normal, the easier it will be to not feel on alert all the time.