Just some more thoughts on Wheel Bearings:
Some background: Toyota Motorhomes (should) all have what's called a "full floating" rear axle to carry the load of dual rear wheels and the
weight of a small motorhome. That said, this type of axle DOES NOT get lube from the differential supply, but has bearings that are greased and must be repacked just like trailer wheel bearings.
The connection to FGRV's is that I have seen rear axles with upwards of 75,000 miles that have never been repacked and still show no wear. However, the two bearing failures that I have seen in this application both happened on rigs that had been stored and not moved for years on end, and the grease, for lack of a better word, had caked up and dried out, as had the seals on each side of them.
When I was buying my Hunter C-II, I was told that it had been parked for at least 7 years. As I had a 500 miles tow home I negotiated with an excellent seller, who also just happened to be a mechanic, to not only replace the
tires with something newer, but to also repack the bearings before I got there. (Not only did he do this, he saved the old seals to show me of his work.) As expected, the grease on the south side (the side always towards the sun) had turned into a semi-solid mass and those on the north side were still somewhat greasy(?). Some months later, when I was getting new
tires, I pulled the drums to check the seals and all was well.
Bottom line: Unless it comes with a complete service history, I would suggest starting out ownership of a used FGRV with a bearing repack and new seals at a minimum and, if there is any question, new (never chinese) bearings. that way you know the history of your bearings. And, as Donna mentioned, if it sits a lot, take a few minutes every once in a while, to raise each wheel and give it a spin to move the grease around and prevent getting flat spots (?) on the bearings.
BTW: When replacing bearings, NEVER reuse the old races with new rollers, they don't match and an early failure may result.