I wouldn't worry about changing your plugs before 40 to 50k. Like I said, I changed mine at 41k and will put at LEAST 50k+ on this new set before replacing them. The plugs themselves were still in great condition. By the looks of them, they would have probably lasted the 100k mile change interval....I was just worried about the plugs getting ceased up if I left them in longer then ~ 50k miles. I let all the horror stories get me a bit worried. But after replacing the plugs, there was no corrosion, just some carbon build up between the electrode shaft and the cylinder head. When you change the plugs, follow the TSB.....loosen the plugs about 1/8 turn and let the penetrating lube loosen up the carbon build up. You shouldn't have any issues.....who knows maybe a truck with 100k mile plugs would be okay if the penetrating oil was given enough time to break up the carbon?