OK, I know the Shimano hubs probably weigh progressively less as they become more pricey, but for the average user, is a well-maintained Ultegra hub going to last longer than an equally well-maintained 2200, etc?.

They all use loose balls that are probably the same (certainly after they've been changed at LBS).

Are the races really made of sterner stuff, enough so to be an advantage for average user? How can the cheaper ones "fail" if they are periodically inspected, worn parts replaced, well-greased?

I really kinda think any Shimano hub will outlast me, given proper care. Am I wrong?