I have 23. 5K miles on my pads and have checked them, front and back. The front ones have 3/8" pad showing, with 1/2" on the back ones. I don't have a service manual yet but have noticed that Haynes says to swap them out when they get to 5/16". That seems to be a lot of pad to throw away. Over 50% of my miles involve towing but my trailer only weighs in at 5K.