I chose every 2 months, simply because I went through so many cycles in the past couple of years and have only found a measure of stability over the past three months. I have one or two nasty depressions a year on average, but they seldom last longer than a few weeks.

Mania and hypomania are more of a problem; my basic personality is sort of over-amped anyway, so it's hard for me to figure out when I'm actually hypomanic. It's only when I'm into manic territory that I think hmmm, maybe I'm a little hypo? and of course by that time I'm driving everyone up the wall because I can't sit still or shut up, or I'm ripping people's heads off and shouting down the hole. THAT happens in the spring and summer months and it tends to last awhile.