It's brushless so brush wear isn't a problem, but these motors are air-cooled and will actually be cooler at high speed, low-demand. Lugging it up a hill would be a worst case.
But when the wipers in my car are set to intermittent, they are off most of time and ocassionally off.
(I wish there were a pattern to any of it, since it's often very difficult to fix things that are usually working fine.)