Re-pack wheel bearings

doing it yourself ,every couple years, and new seals. also write the numbers down on the two bearings and seal buy a spare set. bag,em put in your tool box.its not a hard job.

Depends... (Not the Adult wear)

If you tow on dirt roads too Boondock, you will need to repack em more often.
If you frequently drive thru wet areas with some standing water... Same
If your RV is on asphalt or paving, you can go longer between maintenance.

I repack mine every 2-3 years.

If you buy a used RV, repack em, you don't know what conditions the RV has been thru.
(I just bought a 75 Prowler... I towed it home than repacked it the next day.
I also put new rubber on the road... Don't want to be left setting on the side of the road.)

If a new trailer I would certainly grease them at one year old. You'll be surprised how little they have on them from the factory.

After that about every two years. I check mine with an infrared thermometer during my trips and if one or more start to get unusually warm compared to others I'll usually re-grease at the end of the trip or even occasionally while at a campground. Not really much of a job and I carry enough grease/bearing kits for two bearing changes with me.

On a brand new trailer where they have never been repacked I would do it after about a year. After that it kind of depends on usage. If it sits unmoved for a year I would do it yearly. If it gets towed every few months I would do it every couple of years. Cars which used the same system for years recommended after 30 or 60 thousand miles. It's all about getting the grease moving from time to time.
Personally I grease about every 3 or 4 years and so far no problems.