I've done 2 mid-week, spur of the moment flushes. I think after you sort of get the routine down, the mid-week ones work out just fine. I worked all day and had a light breakfast and lunch, and had the ES when it was time, and then the OO (Olive-Oil) at 10, went to sleep, woke up at 6, spent a few hours puttering around (a nice way to put it ;) and then went to work. I have a desk job for the most part, so I was pretty comfortable and didn't have to exert myself. If I had a strenuous job I don't think I could have pulled it off.