Of course the ideal way to check these tapered roller bearings is to raise the axle
, turn the wheel by hand slowly and feel and listen for any grinding and noise. Nobody is going to do it every time they fill up on gas. The time to do this test is when the trailer is put up for winter - another reason to put it up on blocks for the season.
Feeling the hubs for temperature rise is second best, the more probable source of heat there may be the brakes
. Feeling the tires
is important to catch a slow leak, the flexing of sidewalls is the heat source there.
Tapered roller bearings will only get hot when they were overloaded by the installer and remain so in operation. They always must have some small amount of play. Also they will not seize the way journal bearings might, until they are way, way gone.