I generally repack every year but have at times let it go two years - so far, every time, all has looked fine.
I have to admit that sometimes I cheat a little - i.e. I do not remove the back seal and visually inspect the inner race. But I do rotate it with my fingers to ensure motion is smooth.
I also add a little grease by finger to the back race when I do this. So far it has not gotten me into trouble!
Of course to fully inspect the inner race you need to pop out the rear grease seal - and when you do that, the normal recommendation is to fit a new seal.
Pulling the hubs yearly or every two years is also a great opportunity to check the trailer brakes for wear, broken/missing springs, broken wires etc.
I certainly second what was said earlier about checking a used trailer S.A.P. after purchase!
Quite a few years ago I bought a used "Award" trailer from a supposedly reputable RV dealer about 200 miles from my home. After agreeing to buy it, I was told that there was an obligatory "dealer prep" charge of $200!
I asked if that included repacking the bearings and I was told it did, so I was not unhappy to pay the fee.
I used the trailer without incident for a year, including one trip of several thousand miles, then decided I'd better do a repack.
Thank goodness I did! When I pulled the hubs, I found that on every wheel, the grease was hard and caked and the rollers were just starting to spall and break up. I doubt very much that I would have made another long trip without a failure en route.
My suspicion is that the trailer - then maybe 7 years old - had never had the bearings looked at in its life!
I wrote a reasonably polite letter to the RV dealer including pictures of the distressed bearing races and never got as much as an apology! I have absolutely no doubt that they had done nothing to the bearings when I bought it - and I paid the $200 charge!
PS Incidentally, when I bought my AS used - from an AS dealer, I (probably foolishly in light of my earlier experience!) asked them specifically to do a repack for me. They did so.
When I got the invoice I noticed there was no charge for new seals. When i asked about it, I was told that the seals looked fine so they re-used them. Hmmmmmm!
If I buy another used trailer, I will do it myself for sure!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.