Sheesh! 3 to 6 thousand miles?!? That's insane. I don't even change my oil that often.

I've had a mechanic of 30 years tell me that in many cars, you should not change the plugs just to change them. If nothing's wrong, don't mess with them, as you're just as likely to install them improperly (incorrect gap, I guess) as you are to help it in anyway. Now, he was referring to non-performance environment, but still that's a big difference between Tony and that mechanic.