Likely overkill, it actually may cause more problems as it increases the risk of an error when doing it. Once a year (unless you tow many many miles) is over kill, but easy enough to do and gives a chance to check brakes. We don't travel very far or often so I don't even do it yearly.
Perhaps he could get an infrared temp gun and log the hub temps so he would know if one was heating up more than the others? Once he has done this a few times, he should notice that the brakes are fine and the bearings are fine and there is no need to do it as often.
It is good he is doing it too often than not often enough though.. some folks never pack the bearings or check the brakes until there is an expensive problem to fix.