I don't think you would wear out a ball however the parts of the hitch may be a different story.
I Completely clean the inside of the hitch and the ball then use the white grease. Not as messy as regular grease but still messy. I use a ball cover so I do not rub up against the messy ball.
I recalucated and think Jim was off a little, my calculations say it will take 375,995.0001 years.