I've lost track, but I do at least two a year, usually four. So somewhere around 10 - 15, I'd estimate.
My longest is 21, my shortest is 9 (even on that one, I went longer, but I only count 9 days because I went out for a business lunch and had soup on day 9, and immediately went back on the cleanse. But I do think the cleansing stopped when I ate the soup, so I only count 9).