I can understand what you're saying, but my point remains as I have experienced first hand with my own W126s. Age may generally be worse than mileage but at least with certain miles the drivetrain will have much more life in them regardless of how they were used. Several sensors and such will wear faster with more mileage for a given vehicle's age and will be needing replacements. I know this for sure just by reading threads around here on the sensors, motors and tiny but annoying other things owners of higher mileage cars are replacing now which I don't have to worry about as of yet. For instance, I know that my 500SEL won't be needing a valve job or anything quite involving soon because it still has low miles. Even with city-only driving, such a huge service won't be due prematurely. Also, my 300SD was in pretty much prestine condition when I got it, and I didn't pay with my arm and legs for it.

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver