last year when I got my 6K mile service, they noticed the pinion bearing "had some play" and recommended I get it replaced before it fails... I inquired just how much play and would it be wise to replace it right away.. They said it could probably wait till next year.. So, I just got it replaced over the weekend.. No failure (thankfully) but still $500 I didn't want to spend.. Grrrr.
Hopefully it'll be fine for many more miles and I won't ever have to worry about it.