The rear axle on a FWD car is much the same design as your trailer axle. How often do you repack those bearings?
Since it's not until Sept, buy a IR temp gun ($10 on
Ebay) and start checking your tire and bearing temps after a couple hundred miles now. You are looking for something out of the norm... not more than 120 for the bearings and 130 on the sidewall of the tire near the tread on a hot day. Pull into a rest area without using your brakes and start checking your temps to establish a base line. If one is hotter than the rest, it could be a dragging brake, not the bearings.
With a turbo diesel truck there is very little difference in towing in the mountains except for the longer down hills. Use the tow/haul, not your brakes to keep the speed down... you'll be fine.