First option, be hyper-organized: I had an acquaintaince who had a DD of another european make that he drove even in the Canadian winter... and would then go win car shows against trailer queens in the summer. His car looked showroom all the time and was mechanically flawless.
How? He prepared a written maintenance plan and stuck to it. Just about every weekend he would spend at least a half day on the car. He had a schedule for parts replacement based on probable service life (in other words, he replaced stuff before it broke). If no work needed, he would detail it (and I mean detail, seats taken out etc.).
He changed his oil so often, another car club member actually offered to purchase his old motor oil for resuse (I swear it's true).
Second option: Buy from these guys:
Mercedes Motoring