The two main breeds I have bred in the last fifty years have been Arabians and Miniatures.
They have always been out, most of or all of the time.
I have been feeding Beet Pulp since long before it was accepted as a horse feed, since it came in 1 cwt hessian sacks of shreds that we believed we had to soak for at least twelve hours (doesn't do any harm, just is not necessary)
I fed beef stock cubes and beet pulp as main feed as there really was not anything else affordable on the market (I was always careful the beef nuts had no urea in them, though)
I have never had any trouble, at all, with enteroliths, in fact when they came up in conversation a while back I had to google them to make sure I was on the right track!
I soak my BP and pour the water away, possibly this makes a difference, I do not know.
It is also possible that the stress caused by constant stalling, added to overfeeding of BP leads to a situation where enteroliths form more easily, I do not know.
What I do know is that Rabbit is now just past 32 and has so far shown no ill effects from having been fed on a quite large amount of BP, all his life
Wow, 32 is quite good, especially to have had no problems. I agree that being able to leave them out is best for them since they are natural grazing animals. My little guys would like to be out most of the time too; however, our grass is so rich that the vet had told us to let them out only for 1-2 hours at time. If I leave them out longer, they look like helium balloons (LOL), and then they get the runs. I have been feeding about 1 1/2 lbs of beet pulp to each horse every day, one horse gets 2 1/2 lbs, do you think that might be to much? They also get hay, pasture and a cup of Well Solve LS.