At least once a week... it's part of the P90X program I am doing.
And I have learned something interesting from doing it... Yoga is not for wussies! It was more than just tying myself into a knot; it's a hardcore isometric workout! I actually sweat! Even so, maintained a calm face and a calm mind. What's more... all the soreness I had from any previous days' workout disappears, and I actually feel a bit limber again!