Mileage is a factor for all the reasons listed above. Also something to think about is these cars are all 6+ years old. Averaging 15,000 miles per year puts an average 2006 in at 90,000 miles. Mileage is just another consideration in the confusing equation as to weather or not a particular car is for you.
Given the age of our cars, I think lower mileage tends to point to an easier life. But that's just my interpretation.
I also agree that if you intend on keeping your car for a long time, the more miles you put on, the better. You'll know how it's been cared for a majority of it's life.
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A Venza just isn't the same as a ZHP.