Well, I'll defer to my favorite answer: it depends. Since I'm generally the giver (although I absolutely love receiving!), I allow my patient to relax as much as he or she needs to, or likes to. As someone else mentioned, I generally massage or otherwise stimulate the patient after they've been to the toilet, so that they fully relax. Or gently rub and massage their tummy. If they don't further have that feeling to "go" again (which frequently they do), that's when I give the next enema which is always a clear rinse enema. I generally use a weak Dr. Bronner's Peppermint Castile soap solution for the first enema. Then, the next two are rinse enemas.
After the third, my patient is nice and clean, and clean smelling too, and generally feels great. I've found that that's the time they generally prefer to orgasm, which of course can be achieved in many ways. Some prefer it when they're filled, but I always let the patient choose.