I would pull the hub caps to see if the outer bearing is well greased. At 3K miles on a new trailer, the brakes should be adjusted. I have seen new trailers with very little grease on the bearings, and a few that were properly greased. If EZ-lube hubs, just pull the rubber cap, and you will see how much grease is on outer bearing. I know you can't see inner bearing without pulling hub completely, but if factory did a good job on outer, should be good on inner too.
If bearings are greased well from new, you should be good for 12K miles, at that point, or year of ownership, I'd pull hubs, check/service/repack, and then not worry about it for a couple years, unless towing really high miles.
Jerry