I don't see anything wrong with them, but they are pretty unnecessary. How often do you repack the bearings in your other vehicle wheel bearings? If bearings are well packed, and the mis-named "preload" set, they don't really need any maintenance for quite some time. If I did 10,000 miles per year I'd probably do mine every two years, but I don't do that many miles so it's usually four years or so. The mandate for annual bearing repack is a CYA by the builders.
I do my trailer bearings every few years, and have never had any issues with that timetable. YMMV.