I own a total of geeze, probably 5 Montana Cincha mohair girths in both english and western styles. Every one of them is now about 1" longer than when I purchased them. I hand wash them and lay them flat on a bath towel to dry. I have never had one shrink, but only stretch. But I don’t have the endurance models - only the straight models. Maybe the endurance models don’t stretch because they have more stitching???
During trail rides and endurance rides I have noticed that when you cross water, or it’s pouring rain - the horse is sweating heavily, etc… the girths will stretch out so you have to tighten the saddle after awhile.
Also I have a 100% alpaca cinch and that sucker stretched no joke about 3". I am thinking of wrapping the buckles in vetwrap and putting it in the dryer on hot to try to bring it back down to a manageable length.
In the future I will just buy them a little on the short side. These are my favorite girths and I have no interest in using anything else again. They are so lightweight, breathable, the horses love them, and they wear like iron.