interesting Zack et al, I have had the chance to treat many patients in this area and have had them tell me things. The long and short of it is enemas are not the same. Too hot, too long, chemicals (including chlorine) and you can do harm. Doing it a little cool causes contractions, exercises the colon. Have you ever heard of exercise causing lazy muscles?
The truth is that done right, yes people take them for decades with no harm. IE Dr. John Kellogg MD, daily colonics for around 70 years, and still doing surgery at age 91.
However do it wrong once and you can do harm. There are chemicals that hurt, in particular chloring, that kills normal, necessary healthful flora. This can cause problems within and without the colon.
So it is not the number, the quantity (within reason) it is the type and methods of the enema that can increase the quality of health or decrease it.
I had one patient 95, that did daily enemas, few problems in and good health at that age. I had another, age 40, damage to her colon from years of doing too warm coffee enemas.