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.
True, ive never seen a koyo bearing failure, Though I have broken trail jizz bearings. I had 25 year old koyos in my old rig on 40's, never beat on it too bad, but it made it though some of the harder trails in AZ without issue. BUT, I used a trail jizz rebuild kit in my 85's front axle, after 1000 miles and 6-7 medium trails on 35's the drivers upper bearing was broken and the TG tie rod ends were worn really bad for such little use... I now have marlins 25mm kit, arms, and rod ends on both rigs.
Anyone that I have seen in person break a trunion bearing was due to trail jizz bearings or steering arms, only seen one guy break an allpro 17mm pin, but he was running jap bearings and he BEATS hit rig... 250hp turbo motor and 37in sticky crawlers...
