Are the brakes getting really hot? This happened to one of my earlier cars, It was a dodgy caliper, the thing is, If your getting sticky calipers, then the Guide Pins (sliders with the rubber boot on) Want a good clean and grease them. Also take a look at the condition of the bottom of the guide pin. if its mashed, New ones are needed. otherwise you'll end up with the same problem again. but clean them up first mate.
Also put some high temperature copper slip (anti squeel paste) on the back of the pads. (not the frictional side obviously)