mileage for resell is based on the model year @ an average rate of 12K - 13K per year which is the national average per driver according to the the U.S. Dept of Transportation.
something to keep in mind, if you have vehicle that is say a 2007 but you bought the car in 2006 (did this with my wifes car, bought in Sept 2006) those couple of extra months of mileage will hurt you.
my 2005 Chrysler 300c was built and purchased in April 2004, so I had nearly 1 year of extra mileage that hurt me on resell, because even though I had actually owned the vehicle for 7 years, it was actually only 6 model years old. So I had 7 years worth of mileage but it was calculated @ 6 model years. @ 7 years my average was 12142 miles per year, @ 6 years it was 14166 per year and I was dinged for that.
as far as resell mileage is concerned, as long as you are below the national average of 12k per year over the life of the model years of the vehicle then you will have a slight advantage.
but also keep in mind that any vehicle with over 75K regardless of it's age will only net you auction price on a trade it, as most dealerships will not keep vehicles over this mileage on their lots, they will dump them @ auction for the private lots.
"A world 100% full of Prius drivers is still 100% addicted to oil. " ~ E. Musk