Not sure if it's just the aftermarket rebuilds, but these Protege rear calipers are complete junk. On my car every two years, one of them starts leaking or seizing, requiring replacement of the offending caliper, both rotors, and pads. I'd rebuild the caliper, but finding a tool to remove the deeply-recessed snap ring has been an issue. Plus, replacing the seals isn't enough, really the piston should be replaced, too (see the above picture). Aftermarket pistons are available cheaply, but the off-brands selling them don't inspire confidence. The Mazda OEM rear caliper rebuild kit is about $50, but it doesn't include the piston.
AutoZone supplies a lifetime warranty but charges $100 per rear caliper or so. This is probably the best route for someone who is planning to hang on to their Pro for a while. Incidentally, the OEM rebuilds are $300 per caliper, but I'm not sure if these are any better than aftermarket.