I know it goes against the grain of the Master-Cleanse - but it's so hard for me to strive for perfection. Yes, I cheated on day 4, I admit it, and am still begging my body for forgiveness (on this day 5).
We went to a baseball game in a private box and there was food EVERYWHERE - I'm talking the gourmet stuff. Has anyone been to a baseball game while on the cleanse. Well, I decided that was pure torture. Until yesterday I didn't realize how much people stuffed their faces at those games! LOL
I ate a bit of ceasar salad and a glass of wine (HORROR)! I'm not going to beat myself up about it anymore (but did feel a need to confess).
Today I'm back on and am taking it a day at a time :)
To answer your question - I think it's a personal decision and to do what you feel is comfortable for your body. I'd like to do what Robin Quivers (and others on this board have done) and go 21 days on the cleanse!