Anywhere from a few weeks to a few months, depending. I alternate between rapidly cycling and then sometimes more "classic" swings of long lasting mania/hypomania, then into depression.

I do tend to rapidly cycle more in the summer and have longer-lasting depressions in the fall/winter though. In the summer, I used to have longer lasting hypomania/mania, but now my summer pattern tends to be: 1-2 weeks of depression, 1-2 weeks hypo/manic, baseline, then repeat.