I have had 3 times (childhood/teenager, midlife and currently) in my life that i played with my butt, and. I used to play on a regular schedule, sort off, with regular average size toys.
Not sure but about 15 years or so i picked-up my anal endeavors, of which probably 10 years ago i started training for the bigger toys and getting more and more extreme.
I used to aim to train at least every other day. But i didn't have hardly añy overtime at work, currently doing 48 to 72 hours a week in the last 4 years.
I have developed a nice personal record of 3.3 inch diameter stretching and about 20 inch deep on depth play. (1 inch diameter)
Right now i play extreme every week to every month, but little play probably once or twice a week. Usually limited to pool balls insertion.
I have not lost anything in stretching or depth, it's all still the same. I can now insert toys on a first try that i couldn't even get inside year ago, so my body is still trained perfectly.
Not sure how long someone can go without play before he or she loses size etc
I had gender reconstructive surgery in 2017 and did not play anal for almost ¾ of a year, afraid to damage my new vulva, and when i picked up my play, it was like i never stopped.
Hope this gives you an idea.
PS i don't do fisting since i don't have a partner, but would love to try. I do have 3 fist toys that can do their thing.