The pony in me was no where near fully in me and, he lasted maybe 45 seconds leaving me needing human assistance to finish.
There was a lot of horsepower, just no staying power.
The pony could have cared less... but, I now know that once they know their human mare, it does get better... or so I am told.
I've seen studs breed mares a number of times, and I've watched a ton of homemade vids of women getting mounted by ponies. In both cases the length of time for thrusting seems to be about 25 seconds on up to 45 seconds. So, your experience was at the upper end of the range, unless..... you include time of the stud's penis staying in after his orgasm. The flare is still sort of wide for another 30 seconds, more or less, so I can see the penis staying inside the human mare till he back off of her. The ponies usually back off. Standing on hid legs takes a lot of effort. They sometimes stay on the back of a (horse) mare for 10 to 20 seconds looking drowsy and ready to sleep after orgasm.
Regarding injuries
For a human receiving vaginal penetration, the flare is wide and sort of soft. I'm sure some vaginal fissures have happened from a horse penis, but there is unlikely to be a large vaginal fissure from a modest to well endowed pony. I've read accoounts of one gynecologist that wrote in old anatomy book about witnessing only 20 or so vaginal tears up in a vaginal fornix from a long human penis, out of seeing thousands of women over years. It might have been fewer than that. A human penis is more pointy by a long shot. Not that a wide horse penis wouldn't cause pain if angle is bad, or his flare is too wide for her, but it is not likely to feel like a "poking too deep" pain in a vagina.
Anal- The safest thing is to keep the horse peen down in the pelvis and rectum. Again, no guarantees about not getting injured, but most injuries likely happen if the stud's penis goes up deep "around the bend" in the rectum to the descending colon. That curve is more tight.
When penetrating a human vaginally, the horse peen is staying down in the curve of the pelvis, even though it looks deep. This is the pelvic hollow. It's at least somewhat safer to attempt the same with receiving anal, keep the head in the rectum and don't go for deep anal unless he is not near your limit in size. Even then, I bet unexpected accidents can happen.
caikgoch also mentioned keeping the horse peen head down in the rectum too, on a different discussion thread. Play at your own risk......