Based on the data here, which we could call anecdotal, and my own experience of 60 plus years of taking enemas, my observation is, the vast majority of people will not become dependent on enemas. Addicted, I can't buy that either, not like drugs or alcohol.
Just like any form of masturbation, and I think that would be a proper term for what goes on when we enjoy an enema, there are those take them occasionally, and those that take them very frequently, and just like with frequent masturbation, who is to say how often is too often!
I did run into one interesting lady, she was very into enemas after in she first got into the sexual side in her 20's. For about 5 years she took them frequently and then one day she decided she liked them too much. Got guilt feelings about them not being a part of normal sexuality. She stopped taking them, you could no longer even talk with her about them.
Sad what people do to themselves because of the perception of "normal."
My observation, take them as often as you want, as the old saying goes, if it feels good, do it!