I've never had a trailer wheel bearing failure, but I have never put enough distance on any trailer for that to mean anything.
I've never had a wheel bearing failure in a car, but most of my car bearings have been sealed units (which are never repacked). My first car (Toyota Tercel) had rear bearings like a typical trailer, in a combined hub/drum like a trailer; I repacked those only when replacing brake shoes, maybe twice in the 354,000 km (220,000 mile) life of the car - it was retired by body damage, with the original bearings (front and rear) still in fine shape. The other car I had with non-sealed bearings had no problems with them, and although I got it when it was old I didn't drive it for very long.
I did have a front wheel bearing failure on our Chevy truck, with bearings just like a trailer. I don't recall ever repacking those, since it didn't occur to me that a modern vehicle would need this sort of work. The whole truck was - in my opinion - a pile of junk so although the bearing failure was no doubt my fault, it didn't really surprise me.
I have noticed that Dexter offers trailer bearings in an oil bath lube option, which some people really like. While this is rare on light
vehicles, I get the impression that it is common on heavy commercial vehicles, so that may affect how commercial experience applies to repacking the grease in trailer bearings.