how long or how many miles do bearings last?

mosseater wrote:
There are more bearings and seals ruined by mishandling than actual wear and tear, by a wide margin. Keep them clean, repacked, and properly adjusted and they will outlast you.

Here in PA where we have mandatory yearly inspections, each trip to the garage is an opportunity for mishandling, introduction of dirt, too tight or too loose, nicked seals, etc. I find it irritating and unnecessary, but the gubbermint says we have to. It isn't rocket surgery, but it still needs to be done properly.