front brake discs

To me, they were just trying to 'up-sell' you.

Carl

If you are not feeling any pulsation in the brakes, the rotors are probably ok. In general it's not a good idea to machine them unnecessarily as they don't have much extra thickness on them to begin with. Usually they can only be resurfaced once before falling below the minimum allowable thickness (which is stamped on the hub portion of the rotor). However it is possible for rotors on a lightly used vehicle to deteriorate more rapidly than those on a regularly driven one. As the car sits, the rotors build up a layer of rust. On a daily driven car any rust from a night out in the rain, etc. will be quickly swept away after a short distance of driving, but on one that sits the rust will build up and may eventually render the rotor worthless. Ask the shop to show you exactly what is wrong with the rotors, and don't just take their word for it.

I agree with the idea that if you feel no pulsing or steering wheel shaking then the rotors are just fine.

I just did the brakes for the first time on my wife's Forester after 6 years / 72000 miles. REotors measured about .005" less than "new". There WAS a little rust buld-up at the edges of the friction area.

Rotor edge rust outside the pad area is of no consequence nor is slight grooving IMO. If the car has no shimmy/pulsing during braking I'd leave the brakes alone assuming the pad thickness is good.