Thanks for all the responses! Sounds like there's plenty of wear left in the rotors. The car has 33K so it's definitely the first set. I will check the pads and replace accordingly, likewise on the front. The mechanic told me that the fronts only had ~20% wear on them at 29K so I'm willing to bet that they were replaced not long before I bought the car at 25K.

Again, thanks for the advice. The only thing worse than needlessly throwing money at a dealer is failing to do the maintenance at all!