I'm curious....where did it specify that wheel bearings are scheduled for replacement at 20,000 km? Is it in the service manual or owner's manual? I don't recall ever reading anywhere that there was a scheduled replacement for those, and 20,000 km isn't a lot of mileage for a wheel bearing. My V-Strom had 18,000 miles (almost 30,000 km) when I sold it with the original wheel bearings, and my Super Tenere has 60,000 miles (96,000 km), still on the original bearings.
I don't dispute that harsh conditions could shorten bearing life; I was just wondering where a mileage based bearing change was recommended.
Good luck with the Alls Balls; they seem to be hit or miss for a lot of guys who've used them.
"No matter where you go, there you are."