I don't understand rusty discs lasting that long
On many cars I've had, after washing, the discs do go orange after an overnight garage stand, surface rust. As a result I do initially get grinding when going along the driveway (all auto box so using the brakes to crawl) but once out on the road the surface rust soon dissipates.
At my old house I had 1 junction where I normally had to slow or stop. Then a 50mph clear carriageway with a petrol station at the end.
So I braked slightly down the driveway, then light braking at the junction, then braking in the petrol station by which time all grinding had gone.
Looking at the discs they were all shiny silver again
My theory is that the pads run very close to the discs and the slight heat is all that's needed to remove any surface rust