was wondering about that...I have 42k now on my 03 and the plugs supposed were supposed to be changed at 30k miles. I popped the hood and saw the 2 spark plugs per cylinder and decided not to bother. It runs flawless at 42k on the original plugs

 

When I changed my Champion Coppers at 60k they looked fine. Im sure I could have kept running them. But since I was there and had already bought new ones, I went ahead and replaced them. They were 1.79 each and the number on mine was 570