The wheel bearings died on the Jetta at 103kmiles; at 105k I had enough and took it in. Diagnoses was left. When it went up on the rack I asked about the other side, and the mechanic had planned to check. Sure enough, it was gritty, just not making noise. Searching online it seems the MkIV VW's have short lived wheel bearings.
Now I had OEM bearings put in. Maybe they just haven't made noise yet, but for some reason it's noise free after 190kmiles on the replacements (293k on the car). So, if it was a VW I'd recommend doing both at the same time; I guess there isn't much time savings if you do it yourself, but if you are paying a shop and parking the car for a day or more, just do 'em both. Wife's Civic had one go, so we replaced just that; I think the other let go six months later. Go figure.