Just as a sort of unsolicited disclaimer and statement of truth, for shredder, the original OP, and LoveItKinky, who's been asking advice about reaching 4 quarts, and probably a few other skeptics, I'll just offer a few words.
Shredder was reading on Voy about large volume enemas up to say 6 quarts, stating he limits himself to about 3. He also said "My question is, how many enemaphiles really take these high volume enemas, if so do you hold them for long periods, say 20 - 60 minutes and are they painful?"
LoveItKinky says he usually takes 2.5-3 quarts and asks how to safely try to accomodate 4 quarts. Some of us have offered advice.
I'm 67 and have taken recreational/sexual enemas since age 15. That's when I discovered enemas as well as how to give myself an orgasm. Most of mine have been solo, but I've had a few ex-GFs and 2 ex-wives who gave them to me for awhile. I'm a switch, definitively heterosexual, with a strong bent for submission, especially when being given enemas. For decades I took and enjoyed 2-2.5 quarts, thinking it was fairly large and erotic. I joined Zity about four years ago and after reading a lot here decided larger enemas sounded fun so gradually worked up to 4 quarts a couple of years ago. This is my usual sexual enema now, and I took 5 quarts just one time as literally an accidental experiment. Both 4 and 5 quarts go in with no sign of pain from overdistention, just a lot of widespread internal pressure, which I like. I often hold 4 quarts for 30-60 minutes, sometimes longer, simply because it's enjoyable and erotic. I'm not in competition with anyone and never will be as far as any aspect of enemas goes. I've increased my usual capacity simply because I've always liked enemas and distention and enema-induced orgasms and I read here that many members took much larger enemas than I did, and it sounded fun. In fact, it really is fun.
Back when I was taking max 2.5 quarts, 4 quarts seemed excessive and unattainable and frankly a little crazy. Now that I've done 4 many times and 5 just once, 4 obviously feels comfortably large and easily achievable, as does 5. If I wanted to try 6 quarts, it may or may not be achievable but certainly seems at least possible. I've personally read members' posts here that claim to have taken 7, 8, and even 10 quarts of enema.
To answer shredder/OP's original question,
1) yes I take large enemas, so far up to 5 quarts. I'm toying with the idea of trying to do 6 but it may never happen.
2) I retain my 4 quart enemas usually 15-60 minutes simply to enjoy the sensations, the submissive feelings they cause, and the arousal they give me.
3) no, they are absolutely NOT painful, except for some occasional cramping.
I think the main point of this is believability of postings about enemas. I once thought that 4 quarts was beyond belief but now I'm a regular practitioner. And I took 5 once as well. So drawing the line about how much people have taken is difficult to know. You can come to my home and I could easily verify my claim by showing you the measured volumes and then running the 4-5 quarts into me. In other words, I'm telling the truth about my volume intake. Accepting the claims of other members that may seem excessive or not believable might have to come to that as well. Now having done 5 quarts myself, it's not too hard to imagine taking 6, but almost equally believable that I might run into sharp abdominal pain before I get there and quit at my maximum which might top out at 5.3 or 5.5 quarts. At this point I would be pretty skeptical about 8 and 10 quarts, but sometimes truth turns out to be stranger than fiction. I just hope we all play it safe and no one gets injured from this sort of entertainment. I'm satisfied enough with my own physical and psychological sensations from a 4-5 quart enema that I may never go any higher.
Eric