Personally, the manual I have from Lippert says yearly or every 10K miles.
For me, I trust no one's work like I trust mine, so I do it. Yearly. It is really not hard and takes about 3 - 4 hours (I'm slow and methodical). If it is just seals, grease and cotter pins, cost is about $25 - $30. But, I *KNOW* it is done right and I *KNOW* what the condition and adjustment is, and that is priceless.
Here's the procedure.
1 - RV parked on level concrete, unhitched and leveled (6 point electric Level Up)
2 - Once leveled, Manually raise the front 3", then the rear 3". At this point the middle section jacks will be about 2" off the ground. Press the "Auto Level" button and it will ground the front and rear (and immediately determine they are grounded), then it will lower the middle jacks until RV is leveled. At this point the tires are still on the ground, but do not have much weight on them. (My guess would be less than 300lb each)
3 - Break all wheel lugs loose (hand tight).
4 - Using a my bottle jack (12 ton) and four 3 ton jack stands, I raise each wheel about 1" off the ground (requires VERY little effort on the jack) and place the jack stand saddle under the axle, between the U bolts. (My jack stand's saddles have the same radius as the axle, 3", so the weight is evenly supported).
5 - Remove lug nuts, remove wheels.
6 - Remove axle hub end cap, remove cotter pin, remove castle nut and remove outer bearing and drum.
7 - Remove wheel bearing seals and remove inner bearings.
8 - Thoroughly clean and inspect all components and replace as needed. (this includes removing all grease from inside of the hub! Also, grease, seals and cotter pins are always replaced)
9 - Repack wheel bearings and insides of hubs (I use Mobil 1 Synthetic - red). Install inside wheel bearing and install bearing seal (VERY thin coating of grease on inside of lips. The seal, not mine.)
10 - Install hub, outer bearing, washer, nut and tighten to about 10 ft lbs, spin and tighten to 50 fl lbs. Loosen, then hand tighten. Insert cotter pin. (if required, back loosen nut until cotter pin can be installed, NEVER tighten!)
11 - Install wheel and torque to spec.
12 - Remove brake adjustment cover from rear of backing plate.
13 - Manually spin wheel, while adjusting brake until wheel cannot be spun by hand.
14 - Loosen brake adjustment until wheel spins by hand, with a SLIGHT drag.
15 - Lower RV and set tire PSI to spec.
Tina + Dutch and Bell, Bobo, Harley, Buddy (the dogs)
2011 F350 Lariat 4x4 DRW SuperCrew 6.7L (B&W setup w/Air Lift 5000 Ultimate)
2014 Columbus 365RL (Airflex and Voyager package)
Nights Camped 2014 - 154
, 2015 - 32, 2016 - 4