We bought our 4 y/o trailer in 2015. Three axle toyhauler, GVW 21k, 8k hubs/bearings. Unknown history, pull about 5k miles/yr. I check bearings at least yearly for play, adjust as necessary.
Until late 2022, I'd needed to adjust 2 (two) bearings. At that time, I took the trailer to a trusted trailer repair facility, and had a suspension overhaul, along with repacking the bearings. The mechanic said one wheel had a little dirt in the bearings, all others were still perfect.
Since that time, we've pulled another 10-12k miles. Trailer got back into the shop today for a going over and bearing check.
So, my opinion is that if you check for play occasionally, and are well below the load capacity of your hubs, repacking more is a waste of time.
I'll also add, I will not run Bearing Buddys. They only put grease in the outer bearing, until you eventually fill the cavity inside, before any grease gets to the inner bearings. When you pull off a hub, is there generally grease in the cavity? No, because you need that air space for expansion as the hub warms and cools. Fill that void and when the grease cools, it sucks dirt past the seal. Dumb, dumb, dumb.