I tend to buy low mileage slightly used vehicles and keep them til they die, high mileage in my mind doesn't exist, as we can't always afford to replace the vehicle versus the cost of fixing it.
Depending upon what it is that needs fixed of course. Had a toyota pickup that we replaced 2 headgaskets and one engine on, before finally giving it the boot.
However, I agree with many posters here, I've seen more *high mileage* vehicles that are in better shape then their younger counterparts.
I currently have 2 rodeo's, both automatics, one with 350k an the other with 200k - original transmission and engines in both; however we take exceptional care of these trucks and they're not driven harshly by any means. Both trucks run, look and drive as if they're new.
Whereas the lady across the street has a pontiac of some type with only 60k miles, car looks like it's 30yrs old!