I have a 28 ft. TT and had the wheels bearings completely serviced in 2019. I have used the trailer only twice since then for 2 trips of 400 miles total. I would like to make another trip of about eq...
If you trust the shop did it right, just head out.
I might stop at 10-20miles and feel the hub to see if it's hot and then again at 50 miles. If they are cool, you should be golden (this assumes you don't stop at the bottom of a big hill and the brakes are hot from braking).
I am in the habit of doing a walk around when stopping for a bathroom break looking for anything out of place and I usually reach in and touch the hub to check for heat.