I agree with the bent spindle but something else comes to mind.
Is the bearing a "name brand" and even if it is, where was it actually made? I have to change a wheel; bearing on my 85 mustang this weekend, lost count of the number of wheel bearings I've replaced over 25 years.
Even the ones in a box marked "Timken" aren't lasting, maybe it's because they aren't made by Timken ? (Timken plant here in c ow town is long gone and I understand the home plant up in Camnton, OH is a mere shadow of itself).
I'm also having problems with the bearing grease breaking down. Tried the "super gee whiz" space-age red gel grease a few years back and every vehicle which receaved the gel has suffered from bearing failure due to lack of lube.
Another really off the wall problem comes frmo lack of ground between the chassis and battery. GM got hit for a large number of replacements back in the 70's because the ground for the chassis was going through the bearings on the rear axle.
Only other thing that coomes to mind is if you spun the bears when dry after cleaning? Yep, all you have to do is not remove a small spec of hidden dirt and it will destroy the bearing. Same thing applies to dirt getting past the dust and grease sheilds. (But explain how cars from the 30's, 40's, and 50's managed to survive being driven for years missing a hub cover on the front wheels???)
Check the spindle, make certain the wheel race is in fact being held in place by the hub. | 
