disc/drum diagnosis help needed

I just had pads that were eating up the rotor on the passenger side of my Ram. Bottom line the 20 year old caliper piston was frozen and would not retract. New calipers, pads and rotors fixed me up. By the way the new calipers have a plastic piston which will probably prevent this from happening again. Don't think I'll get another 20 years out of the truck though.