For a vehicle which has multiple owners it's easy - it's the average usage over all owners which will matter. My first comment was about emissions over a fixed

For a vehicle which has multiple owners it's easy - it's the average usage over all owners which will matter. My first comment was about emissions over a fixed amount of time. You could instead assume all vehicles lasted for a fixed number of miles instead of a fixed amount of time. If you do that (and you assume the vehicle lasts say 100k miles) then I suspect the EV would always be the greenest over its life. However, since we know that both the age of a car as well as it's mileage influence how usable it is I think my main point still stands. There's a range of levels of greenness which will depend on how you use and maintain your car.