I have never lubes on my Montego bay and haven't had any problems with them. I check them before every trip for play and oil seepage. Parts are hard to find so I carry a spare hub and a spare bearing with me. If I have spare parts, I will be less likely to continue and taking a chance on a bearing I suspect is going bad. I plan to replace my bearings when I replace my tires next year.
I have had standard axle bearings fail. I believe trailer axle bearing failures are fairly common and is the reason why most RVers are so anal about preventive maintenance.