Depression? Maybe 18 months. Hypomania - a little over 2 months and counting is the most but that is current and at a level I am good with. The upward spikes that are not so good in the past were usually only 5 or 6 days and I don't think I ever went more than 2 weeks. For nearly 25 years until about 2 months ago my cycle was depression for months (often over a year) interrupted by brief hypomanic episodes. I do not know this stability of which many people speak. That's why I am very pleased with current meds keeping me slightly hypomanic.