My last Edition 30 08 Plate which had only covered 43K Miles had a NSR Caliper at 39K Miles due to binding.
I also had to put a pair of Rear Calipers on my Skoda Fabia VRS, 70K Miles and a 55 Plate. Although the Pistons where sticking it had the opposite effect on that car though as the Handbrake was non existent with loads of free play in the lever and a big rusty lip on the Brake Discs.
Both cars have a very similarly designed TRW Caliper, I put new TRW's back on too and they came pre-painted.
Depends what the issue is with your Calipers but if the Pistons wont go back then its replacement time.
What I would advise if the Discs have got too hot and discoloured they could have possibly warped if they have got hot enough due to the binding then I would replace the Calipers, Discs, Pads and also the Brake Fluid.