If they are working fine, why do you think they need to be replaced?
If the rotors are glazed, as it sounds like your are describing, you can take the pads off and sand the pads and rotors to remove the glaze. In extreme cases, you may need to remove the rotors and have them machined to get rid of the glaze. If you machine or replace the rotors, it would be best to replace the pads.
But if they are working fine, it would be a waste of time and money to go any further. Usually you don't need to worry about glazed pads and rotors unless you are trying to get rid of a noise.
