I've had my Z for two weeks now, from what I notice that the cloth interior gets whitish like sweat stain but when I washed my car today I wiped down the cloth seats with a damp towel and shwing it's all gone and it brings it back to it's original color. And I try to be as careful getting in / out of the car but sometimes you forget I'd say I'm more forgetful than careful sometimes
I think with proper care (cleaning / wiping it down) the seats should last a long time.