I was amazed last night when I inspected the rear bearings - they look brand new after 15 yrs work- there wasn't even a hint of corrosion on the bearing nut thanks to that little hub cap design.

Does the grease have a usable life before it should be replenished?

 

I think most of it depends on the bearing. I know on our race car trailer, we had problems with the brakes sticking and it use to destroy the wheel bearings. The grease would overheat and the bearing would get destroyed. Road side wheel bearing repairs are never fun..

That said, ive pulled wheel bearings out of WD21 pathfinders, actually did one today, a 91 that has never had its wheel bearings replaced AFAIK, and they looked fine, no visable wear, grease was dirty, but otherwise okay.