Wow, that is quite a trip just to go to Gratten.
My trailer has tiny wheels. I did put on bearing buddies when it was new and make sure they are full of lube, but I've had no problems. I've put thousands of miles on it. I sometimes do 80 with it for a couple of hours or more. It does get warm, but not hot. Just warm to the touch. It doesn't keep getting warmer and warmer. It reaches a steady state and just stays there. After all, it does no braking, no force goes into that tire expect for holding up the weight of the trailer and the bike. Once you're up on the interstate, it's just coasting.
I do make sure that the lug bolts are tight, the bearings are well lubed, and that the tire pressure is high. Those tiny tires have a recommended pressure of what, 65 lbs? The higher the pressure, the cooler they will run. I run it close to the maximum, I think 5 pounds under. It also tows lighter.
In case someone out there is interested...
The bearing buddie is a spring loaded cylinder full of lube that continually pushes lube into your bearing. It fits where the bearing dust cover would go. It has a zerk fitting to let you fill it up with a grease gun.