According to the maintenance schedule on my truck I change air filters every 75,000 miles.?

It really depends on where you drive it. If you drive it around in a rock quarry, then probably every 15,000. I go by the solar method. I take out the air filter and hold it up to the sun and if I can see the sun clearly, it's still clean. If it looks like the last eclipse, then it's time to change it.

Like above said, there really isn't any guidelines or mileage on air filters replacement. Usually it should be checked at every oil change & if its dirty, replace it. I think 75,000 miles is a little too far in between on replacement though.------------Every owners manual if you look in one will tell you if you live in dusty climates to replace it every 3,000 miles