00 2.5RS wheel bearing

I had my left rear wheel bearing replaced in February. (2nd time in 3 years) In July, the road noise started up again and I took it back to the shop to do a warranty claim on the part. They replaced it, and now the road noise is back. I'm convinced I have bad luck and gotten bad wheel bearings, but my guy says there's got to be something else causing the bearing to go bad so quickly. I've owned the car for 6 years and the left rear bearing is the only one thats gone out, 4 times now.
I don't drive the car hard, it's used as a daily commuter for about a 6 mile roundtrip.

Any ideas on what it might be to make a bearing go bad quicker?

So I talked with a subaru mechanic. He said the problem could be the bearing housing could be warped, or it could be the way the previous mechanic installed it. I will be taking it in to find out. I will post the solution when I found out.

I would go with the installed wrong option. I see a lot of rear wheel bearings replaced, none come back without some mileage on em. And the knuckle that they go in is pretty solid, if anything it would crack before anything else would happen.