Differences that might explain why the rear wheel bearing races are lasting so much longer:
-Larger bearings (1/4" vs 3/16" for a larger contact patch, less stress on the cone)
-More braking load on the front wheel
-Occasional front fork chatter which may stress the hubs
Anyway, I packed everything with grease, buttoned it back up and lubed the drivetrain. Now she purrs like a kitten.