Mia, I asked my CDC this same question, and she said 'it's your diet - if it works for you, do it'. She also said some of her clients SS all week then 790 at the weekend. her attitude was that as long as you lose weight, you can stick to it and it works, it's okay. I don't know if that's strictly CD policy, but I reckon a lot of this diet is about trusting yourself within what you know works for you and what you can live with, as well as the guidelines.
I know that conversation with her was my turning point on the diet - I was finding strict SS impossible , about to give everything up, and was kicking up and breaking the diet all over the place because I felt I had no control and couldn't listen to my own instincts. I 790 most of the time these days but SS on the days I feel it's right for me, and I'm losing about 3 lb a week...also feel I can stick with this now for as long as I need to. Result!
Just my own experience ... we have to find what works for us.