According to the Al-Ko maintenance manual that is loaded on their website, all axles from 500# to 7000# need to be disassembled and inspected every 12,000 miles or 12 months
(Whichever comes first). This includes removing and inspecting the brakes and bearings and repacking the bearings. See page 11 of the attachment for a summary.
Also, right after discussion how to use the Ultra-lube in the manual, it states the following: "Hubs and components should also be disassembled yearly and inspected for worn or otherwise damaged parts."
Al-Ko Maintenance DocumentFor those of you who think you don't need to do this PM because you don't put very many miles on are deluding yourself. Grease breaks down with age and exposure to the environment.
For those who think you can just inject a dollop of grease every few years, I'll try not to snicker when I see you limping down the road with a frozen bearing.