I have a few, they have been my most durable. I have only broke the 1/2 flex head after 10 HARD years. For comparison, my less than year old dual 80 just got a kit. That one has never seen a cheater bar. The 36 tooth got cheaters and jumped on many times when I was repairing oilfield eqiupment
I think I bent the housing on the 36 tooth though. It turns VERY hard after the rebuild. I dont want to trade it out since it has made me so much money. I feel it has earned a permanent place being only lighty used.