Why would miles be necessarily correlated with starter life? Seems to me the pertinent factor would be number of starter activations. One car might generally get started once and drive all day, another might get started dozens of times a day.
But yeah, there's no start counter (that you can get at, though there's probably one in the car's computer), so when the odometer is the only thing you have to go by...
And, you guys realize that in electric vehicles, the starter has grown (in broad terms) to become the actual means of propulsion, and someday people will look back at internal combustion engines and consider them weird.