You are oversleeping because that is how your depression manifests. I was the same on 900mg lithium. While manic I slept a little, but on the other end, I slept 12 hours including naps. That is a sign of depression. I started on Abilify and now I don't sleep that much. 7-8 hours or less is more to my age (62) - lucky I do not have a job to perform or I would have been in trouble.