[fredjacksonsan]

It does sound like there may be something more that the bearings. When installing, they're being packed with grease, right?

You said off road a lot....how much is a lot, and how rough are the roads? Are you fording deep water frequently? Water can get into your wheel bearings and contaminate the grease, greatly shortening their life.

I'd also check at the parts counter next time for some heavier duty bearings if they're available.