What KF said!
I bet bearing failure is the #1 cause of most trailer breakdowns ;)
Many people only use them locally, the bearings don't really get a chance to heat up. A long drive at highway speeds is another matter.
Best bet if you haven't already, is to pull wheels, grease/check bearings, and maybe spring for a Bearing Buddy or similar item.
Every deer season, I-75 is littered here in MI with camp trailers that lost a wheel or seized up and overturned due to bearing failure.