How long in between cleansing?

I completed 7 days on Master-Cleanse about 3 weeks ago. I wanted to do 10 days but I had to travel and decided to quit after 7. I got a lot out of my 7 days (in more ways than one!) but don't feel that I got the full benefits that 10 days would have given me. So, my question is this... How long should I wait before I cleanse again?