My cousin had never lube bearings on his trailer and after several thousand miles and a few trips into the West he had catastrophic failure in Colorado. He pulled the wheel and somehow tied the axle up as high as he could get it before limping several miles to the nearest town. A new bearing was very hard to find and then he realized a new problem. How to press the bearing into the hub?? It seems this bearing is pressed so tightly that it is impossible to do it without a hydraulic press!!! He was very lucky to have realized the bearing failed and pulled the wheel before it ruined the spindle on the axle.
They were stranded for two days and ended up driving many miles to first find a bearing and then finding a shop with a hydraulic press. After his return home he replaced the other three bearings and bought a spare wheel and bearing assembly. He said he would never again run with sealed bearings because the heat generated by the trailer brakes can eventually destroy the seals on sealed bearings and it happens so slowly that you do not realize it. The ability to pull the wheels, replace seals and inspect or repack bearings is critical!!! Sealed bearings are used on cars and trucks all the time and rarely fail. Apparently on trailers these bearings are smaller and unable to hold up to the heat of braking.