Air Brake Disc Rotor problems of the 2000 Chevrolet Suburban

We experienced problems with the brakes on our 2000 Suburban last fall and took it in for work. We were told the rear rotors were completely rusted and would need replacement, and the front rotors required significant machining to repair. The brakes still weren't right, and we noticed the antilocks were kicking in even on slow dry stops. The dealer discovered the antilock unit was defective and replaced it. We've begun noticing 'grabbiness' in the brakes and took it back in. After only 10,000 miles since putting new rear rotors on, we again need new rotors. The first time we were told trucks from the northeast (we bought it at an upstate NY dealer) always needed new rotors because of all the salt. The truck has maybe been in NY for 20% of its lifespan. This most recent time we were asked if we had been trailing a boat in the outer banks. We were charged $800 the first time to repair this and now, 10,000 miles later we're being charged another $1200.