Those using the Gerson Therapy, described in the book of the same title, have up to 4 coffee enemas per day. I know people who have beat their cancer and are in "maintenance mode" of one per day. I hear of no side effects from them.
I tried the Gerson approach for a while but it's a very intense method for parasite removal. When doing this I had no problems doing them daily. It takes time and supposedly can be addicting, but I quit cold turkey with no problem except for a detox headache. I'd recommend tapering off to avoid the headache.