I have been on the ketogenic diet on/off since February. I stopped for about a month and am got back.
After some research though, I'm considering changing it up a little. Keeping the same principles, but instead of a re-feed, I would eat carbs pre and post workout only.
I am at about 15-16% body fat right now, I have read the benefits of cycling @ about 12% bodyfat, so I want to go as long until I am about 12%, so lets say probably 2 months? Which will coincide well with researching and putting together a good first cycle, etc.
As far as my preference, for certain body parts (legs) I feel better doing once a week, since I can hardly walk the day after. But for the rest of the body, I feel like I can hit it twice a week. My chest, shoulders, arms, abs recover fairly quickly. Usually back soreness can be felt throughout the week, so back twice a week might be overkill.