I also give this idea I have on the bearing failure...

they dont take side loading well from what I have read and been told...

mine was pushing 8-9 yrs at 90 miles a day

I hauled a tow dolly about 200 miles,it had a fishtail motion when empty

wagged my truck the 200 miles back and forth all the way till loaded then towed it like on glass..real smooth and no fishtailing

I think the back and forth did the bearing in, cause of the side loading back and forth

it was bad enuff empty to slow me down from 60 to 45 mph

couple days later it was leaking

I have done lots of hard cornering,dough nuts,power slides,and just plane hammering on it

I think the 200 miles of steady back and forth side loaded them enuff to wear the 8-9 yr old bearing out...

just my experiance with them

my new set is working fine and no leaks with just the o-ring on the bearing...no axle tube seals in this go round