We've had the ultra white seats in our 2017 S 100D since March last year and almost 25K miles - and the seats are still in perfect condition - no visible wear - not stains or marks.
When we enter the car with damp, sweaty or dirty clothing, we will cover the seats temporarily to protect them - and that's been enough to avoid any staining of the seats.
Rather than spending a lot of $$$ for temporary seat covers (which we use just for short drives, before we get changed), we purchased two ultra white bath sheets and a snap kit from Hobby Lobby (to install snaps to loop the towels over the headrests). We did this with our 2012 S P85, and those seats were still in great condition when we traded it in last month after almost 100K miles.
We've had such a great experience with the ultra white seats, that we included them in the purchase of our new X 100D (delivered last month) - and bought another set of ultra white bath sheets to use as temporary seat covers.
We also carry a pack of baby wipes in both of our ultra white interior Tesla's - and if we notice a smudge or mark, we've been able to quickly remove them using the wipes.
Others are reporting similar positive experiences with the ultra white seats. The local Tesla store told us the non-leather premium seats hold up better in their demonstration vehicles.
So it's possible to get the ultra white seats - and keep them ultra white...