Re: New rotors already?!
Are they saying the rotors are rusting?
As in the braking surface of the rotors?
If you look at your rotors after a car wash, mud puddle run, etc. they rust on the braking surface. And a few brake stops later, it is all gone.
I'm running just under 50K miles and the dealer said I had all sorts of pad life left, even though I tend to hang out on mountain highways pretty much every weekend, but a lot depends on your driving style.
A lot of places will now want to replace rotors with pads rather than trying to turn them smooth without going below thickness.
If you want a second opinion, ask a brakes plus tech...