Mine varies greatly, I've had it for as little as weeks and as long as 4 months (and counting). I've also gone from dysthymia to full-out suicidal attempts. If I remember correctly, my first experience with mood disorders was 3 years ago and started off with a very brief hypomanic episode that ended up in my arrest. This quickly threw me into depression that lasted about a month and saw me on the top floor of an apartment block. This year I've been depressed from April to early July, when I had a week-long hypomania before crashing back to the 11th floor of a building again, and I've gotten progressively better but the depression is still ongoing even now.

I find that my depression isn't the same intensity throughout and usually is at a 6-8 (on a scale of 1-10), but can spike to a 9-10 when there are environmental triggers. Some days I can even be at a 4-5, but if it does not last for more than a week I know I'm not actually on a upswing.

How about you?