Actually, there can be a good bit of wear if there is significant pin weight. It all depends on how well you maintain the hitch and the miles (including road quality) on the rig. The manual for our PullRite OE 18K calls for pulling the head and greasing the load-bearing points at specified intervals. This turns out to be about twice a year for us (full-timers with about 12K miles per year). I can tell there's over 3,000 lbs. on the pin when I pull things apart (shiny areas on the load-bearing surfaces), but keeping things clean and well lubricated, the hitch looks like it's got a lot of life left in it.
Rob