Me either... I have run a bunch of heavy Ford trucks over the years, I don't remember doing the wheel bearings more than every 50,000 miles or so unless there was an issue. I do know that on the heavier trucks the rear wheel bearings are oil bath.
According to my owner's manual (you should have one for the chassis from Ford) you should repack the front wheel bearings (and replace seals) at 30,000 miles and change the rear end fluid at 50,000 miles.
Aaron