Your dealer is B.S.ing you!!! You only need to replace the rotors under three conditions beside they are worn: 1: If they are badly grooved from the old pads. 2: They are warped. 3: You are installing racing brake pads which most of them need a new rotor surface. I don't believe in re-surface them anymore because you more likely to get two different thinkness rotors when is done. ie: left rotor is thinner than the right...etc.