I remember wondering exactly the same thing after a couple of months' "stability". Maybe I wasn't bipolar after all---maybe I was just going through an existential crisis and had finally snapped out of it.

I was rewarded for this thinking with one of my worst manic episodes followed swiftly by a hard crash. So much for THAT idea!

If you were stable for 10 years on lithium, have you thought that maybe it's because the medication was keeping you that way, and to go off of it might de-stabilize you? You've logged four months this time.....that's not long enough to consider coming off meds. Of course, it's ultimately your decision but your loved ones, friends, co-workers etc. also have to deal with you, medicated or unmedicated. Just saying.....