1999 Chevy Tahoe Rear Axle Seal - 2500/4WD

I have replaced rear axle seals and bearings, setting bearing load per GM specs. The passenger side seal has failed twice within 100 miles or less. The rear axle has adequate Royal Purple synthetic lube. A light coating of high-temp bearing lube as applied to all surfaces, including the seal. The axle appears straight and the end play (in-out) seems the same as the driver side. The bearing and seal surfaces on the housing seem smooth with noi damage? Is the root cause a bent axle or too much axle end play (in-out). Ideas?

updated 5-11-09
Thank you for the follow up. The surface where the seal rides is smooth with no groove. When I put a dial indicator on the surface where the drum mounts, I had about 0.010 run out. This is on the passenger side. The driver side surface shows.001 to.002 run out. This is an unloaded test. When I figure the run out at the 32 inch tire diameter, its about a 1/8 inch. I am getting a replacement axle for the passenger side.

updated5-26-09
I replaced the seal and the passenger side rear axle. The axle seal failed again after about 50 or 60 miles of driving (better than the previous distance of about 20 miles). I checked with NAPA to see if there is bearing saver for the full float axle, and it appears there are none. Are you aware of any from Timpken or Federal Mogul? I carefully checked the axle tube and seal surface, applying a light coat of high temp bearing lube after replacing the seal and axle. I set the bearing pre-load to torque specs and backed off about a 1/4 turn to slide the key in the slot and installed the retainer ring. Are there any specs on in-out play of the axle. Checking runout on the surface where the drum mounts is now about the same as the driver -.001 to.002. After installation, the axle can be pulled in or out about 1/8 inch. Is that normal? It is obvious at some point someone has worked on the rear axles. Is there only one hub that carries the bearings? Even though the bearing cups seat flush against their machined lips inside the hub, it just seems the axle can move in and out to much? Any ideas at all or other references. Happy to make a donation again.