I've had my rotors replaced at around 5K. My reason was that there was pulsing when I would brake lightly from higher speed, 65-80 MPH. They also replaced my pads.
I wouldn't worry about replacing the rotors unless you can feel the pulsing from the steering wheel. It will eventually happen, but whether if it's sooner or later, that depends on your driving behavior.
PS since you got new pads on now, I'd look at bedding them in.
http://www.zeckhausen.com/bedding_in_brakes.htm