It hasn't been more than a day since I asked this question, but I feel like so far I have gotten AWFUL advice on the topic, from an article about death by vaginal fisting, to "unless you're pregnant and dilating, I wouldn't."
Okay, how about knowing what you're talking about before you give advice?
After getting annoyed with the awful advice I got here, I did more research into the topic. Here is what I found at
The "Cindy and Joe" Data Archive.
There are many medical problems where fisting should not be done. Mostly these are not so common, but they exist. Sometimes previous surgery, low hormones, infections, radiation treatments, and advanced age can be contraindications altogether.
As to loss of sensation, most who practice Kegel exercises do not experience that. If you wish your wife to be very tight at times, and at other times do fisting, make sure she does enough Kegel exercises every day to maintain that ability.
Those who do not do exercises are more apt to have a possible looseness and trouble feeling a penis as well as before. Many couples that do fisting do not mind that at all. If they do, these couples usually use a "spoon position" with the penis and a hand "both" in the vagina at the same time. That way they avoid diminished sensation problems and both can get stimulation at the same time.
So in summary I don't feel that I have experienced any negative effects of fisting, even though my cunt has become loose as a result of my failure to do the Kegel exercises consistently.
Now as to physical benefits, that is mostly in making it easier for childbirth with less likelyhood of tears and surgery at that time. Specifically with those who do regular associated Kegels (as many do) it helps with vaginal tone and sometimes with the bladder function. It is often helpful in those who suffer constipation.
For women who like fisting, they tell me that it is the very best sex they've ever had, by a significant margin. :-)
I really hope that those who replied to my post trying to help in turn help themselves to understand that when giving advice, make sure that it is CORRECT. Please. It appears that most of the questions on this site are asked by impressionable, unknowledgable, young people, and I do NOT want to see them getting bad advice! Back it up with evidence and make sure that your answer is, indeed, a correct one.