Trailers spend a lot more days out of a year just sitting in one place. This is not necessarily good for bearings or keeping the grease distributed over the bearing surfaces. I had to replace the bearings on one side of our Bigfoot
because of pitting, probably a result of moisture and corrosion. I suspect the bearings had not been repacked. Repacking every 2 years will reduce your chances of spoiling a trip with bearing problems. The brakes
should be checked and adjusted at the same time. Disclosure: My family owned a brake shop.