Depends on the amount of warmness that you are feeling. I'll check mine when I make stops on long trips. They will all be warm enough that I don't want to leave my hand there. But if I have one that is hot, while the others are just warm, I know I have an issue.

By the way...I'll check mine on short trips also. Usually when I arrive or get home.

If it's a used trailer, the first order of business would be to pull the wheels and hubs. The bearings, seals and brakes should be inspected and repaired if necessary. The bearings and races should be cleaned before inspection. If they are in good shape, the bearings should be repacked and reinstalled. Synthetic greases will reduce the friction and lower the hub temperatures.

The amount of heat from a properly running bearing should be nominal, not uncomfortable to the touch. The brakes drums should only be warm directly after being used, and cool after 10 minutes or so.

The heat transferred from the tires to the outer part of the rims can be uncomfortable to touch on a hot day, a substantial trip, and heavy load.

If the rims or wheel hub areas are HOT during the normal course of a trip, you may have a dragging brake shoe, a poorly lubricated bearing or an inderinflated tire. It is cause for concern, and the problem should be identified and corrected before you continue.

Good luck with your "new" trailer