My stock bearings that, as far as I know have not been rebuilt since I've owned my 85 truck, has survived the Rubicon and more than five full weeks in Moab. The axle originally came in my 85 truck that I purchased around 2000 and also survived a couple summers of Colorado wheeling. I've run 32, 33 and now 35 inch tires so it's not quite the same as the guys running really big tires, but the stock bearings hold up as long as you don't abuse your truck.
