I'm like several people in that mine has been for about 3 years straight now, but there is a pattern to my major depressive symptoms. It is a pattern that the last therapist picked up on, but since I was a kid it's been increasing in duration and frequency; at 16, then at 25, then at 32 and then the last at 37. This last "episode" though seems to be permanent and I'll probably be on meds the rest of my life.