I dunno, we're not talking about building a nuclear sub, here, it's only axle bearings. I can see where there would be failures due to the Mfg. using axle parts that are right up to the weight carrying maximum. A radical misalignment might cause a premature failure, also. Eliminate those two causes and the failure rate should drop to almost zero. Some have posted in this thread about having just such a history.
For those folks that are skittish, a well respected trailer shop would be my target for getting good service.