It depends. Depressions usually happen in the fall/winter and last months, though the severity of the depression changes throughout the episode and I do have days where I feel normal or even hypomanic. Mania lasts for much less time, few hours to a few weeks. I used to high periods that lasted for months. I miss that.

I had mostly mixed episodes on prozac. It was awful. This winter/spring was the worst depression I ever had, but at least it was a pure depression. None of this weird mixed stuff.