I only did 15 minutes. It's really challenging! I'd have seen it through to at least the thirty minute mark (its an hour + thirty minutes in total) but I'm going to a movie soon and I was starting to SWEAT! Maybe some of you that take more intense yoga classes are saying to yourself 'no duh..'. The ones I've tried, though, have all been about an hour long gentle stretch session. So shocked but pleased. This is something that I'd like to do, possibly every day.
My advice to anyone new to fitness trying a new exercise program, especially yoga, is just do it. Then, the second it becomes too challenging or especially starts to hurt, stop. Don't injure yourself and take caution. But there is no shame, in my books, in doing only 15 minutes and then having to call it quits! Maybe next time I'll hit 16 :)
unrelated but necessary ^