I was diagnosed in 2007 and each year I get better at managing the illness. I have found a good combo of meds and have been on it since May 2010. I still have some mood changes, but it's nothing near what I was like before I was diagnosed. I think it's the nature of the illness and it also depends on outside factors. For me my job can be stressful and I work shift work, so that can trigger an episode.
I hope you find a combo of meds that works for you.