I'm 72 yo and have owned and towed stock trailers, car trailers, boat trailers, and travel trailer all of life
My TTs have put many miles on unimproved FS roads.
The only bearings I ever lost was on a boat trailer that was in and out of the ocean almost every weekend in S Ca..
I repack them when they start running a little warm.
It's been 3 years since I have repacked the bearings on my sail boat trailer.
I guess my comment is I wish EVERYTHING on trailers were as trouble free and dependable as wheel bearings.