If the pads and rotors are fine, why replace them? All my MB's have made noises from the brakes even when in good shape, depending on the amount of dust/dirt/etc. is present.
Have 'em checked (front too, to be safe) and if they're not worn out, drive the car. The rear pads on my C230 have about 1/3 left and are quite noisy now (winter means road grime, etc.) but I'm certainly not going to chuck good pads in an effort to make them quiet.
ASR/ESP equipped cars can be very hard on the rear pads if you use the system lots, and they have pad sensors (one or two?) in the rear.
Also, for those that need new pads at low miles despite no noise or warning light, if it's not you checking the pad thickness, ask to see the pads in the caliper before authorizing replacement. One of my local dealers told me my rear pads and rotors were shot at 60K. The pads were down to about 15%, but the rotors had lots left. The mechanic stated that they used a more conservative measurement than MB "to be safe." BS. I changed the pads and kept the rotors in. At 153K the rear rotors are still within spec and the second set of pads has about 1/3 remaining. It seems some dealers see pads below 50% or rotors below 50% and immediately call to tell you they're shot.
1998 C230 "Black Betty"