Same goes for every component of the suspension, bushings, balljoints. The steering system… Not that steering racks wear out hahah. Could go either way for paint abuse, it will see more rock chips and such but beign on the highway means your putting those miles on the car in much less time than in the city so your spending less time with the car outdoors in the sun. There are TONS of little things you can think of to be plusses to highway milage if you really sit down to think about it.