My Tregg hitch is now 8 years old and have been travelling around Australia in bad conditions and no wear at all. The block does not touch anything as it has pressed in brass bushes that the pivot bolts go through.
http://www.go.jeep-xj.info/HowtoTrailercoupling.htm
http://www.go.jeep-xj.info/HowtoTrailercoupling.htm