I just replaced two sets of wheel bearings after 10,000 miles on my Keystone Alpine, 2012. I had about 6000 miles on it before my last trip and while preparing for that trip I checked all wheels. I ...
I been using trailers for a long time, and about the only one I would repack at least once a year or more was my boat trailer. Otherwise, inspect annually and repack at least every 2 years for the car trailers. I suspect the same with the 5th wheel.