Did you pull the hubs off to clean and repack the bearings and relace the axle seals, or do you have dust caps with grease fittings? I do not like the grease fittings. If you pumped a full grease tube in each hub, they are totally full. There is a grease well in the center of each hub that holds grease. As the hub warms up driving down the road the grease melts a little and some can flow into the bearing as it requires it.
When you pump it totally full the grease rotates in like layers with friction which heats the grease. Eventually it can get hot enough to be like gear oil. It can get hot enough to be like a torque converter in stall for an extended time, big heat.
Semis trailer bearings run with gear oil. The hub caps have a clear center so you can see the oil level and the center has a rubber bung to add oil. There is an "embossed" area to indicate the full level.
I do not know why there is not an equivalent for car and RV trailers.