Every time you stop for gas, feel the hubs with your fingertips. Should be warm (not hot), and all about the same temperature. If one feels noticeably warmer, it probably should be checked out.
I serviced mine after the first year of travel (about 20k miles) and all looked fine. Replaced the seals, cleaned out and replaced the grease with new.
I haven't serviced them again since then (two years now, and another 20k miles or so). I just feel them when I stop, and they are never hot.
I know it's recommended to service them every year or 12k miles, but I'm ok with a longer interval. Heck,how often do car and truck hubs get serviced? As long as I'm not submerging the hubs in water, I think they'll be ok for quite a while. Just my opinion, and not advice.
2011 Dodge Ram 1500 HEMI Quad Cab
2011 Jay Flight 26BH