Just thought I would add that if your changing discs it is highly recommended you put in new pads irrespective of the life left in the old ones. This is to ensure that the surface contact is completely flat during the bedding in process, as your old pads will have been shaped by your old discs. Should you wish to cut corners you might be able to get the old pads skimmed to ensure they are flat.
Personally, when changing discs, I just accept you have to buy new pads, when your paying that much for discs you don't want to screw them up in the first few months...
