Some I did , some I bought them used and added mown miles ; often buying at 5-0100K then adding another 200K of my own . It is a bit of everything you posted .Genuine question. What is it with driving a car to such high miles. Frugality, the challenge of doing the distance or like old cars? I’m assuming you did not put all the miles on the cars.
I usually get bored with a car after a couple of years (also why I frequently change brands) but with my SLK (which was a daily driver) and now my SL, I just never get bored driving it.