I had a set of 31s and didn't have a very good experience. These came from a shop (now closed) in Longmont.
One totally delaminated on an early spring trip to Moab. The second was a sidewall blow out in Boulder Canyon, with multiple open cracks. The third, and final, was on the highway and had a chunk come out of the center tread about the size of a softball.
All three incidents were at or under 60mph and none were in the summer.
That was enough for me. Ever since, I have never considered retreads.