I'm 7 years out. I had one period of small regain - 8 pounds, after my dad died and while I was suffering postpartum depression. It was solely due to poor eating habits.
Regain is due to not overcoming the initial causes of our obesity. Eating around the sleeve. Yes, injury, illness or medication can be responsible - I don't want to rule that out. But most often, when you see regain, it's slider foods, not eating by the hierarchy so you feel full faster and you eat more, and just plain eating crap. Binges and grazing, emotional or mindless eating - if you don't fix this, you don't get long term success. Period. It becomes a struggle to stay at goal.
I fought hard for my new habits. I think every time I put food in my mouth. My diet is carefully selected to be balanced and nutritious; I avoid binges, I don't graze. With this, I maintain successfully and have for years now.
I had therapy. I firmly believe that many of us need to deal with what's under the fat and causing us to overeat in order to achieve this level of success and to stop looking at food for solace.
Cheri