Cooling system for Protege ES

I have a 2002 Mazda Protege ES model. The car has had no problems, except: major cooling system issues. I just got word that my second radiator needs replacing due to leaking. The last one was installed 4 years ago. After changing the timing belt as required maintenence about 2 years ago, they also replaced the water pump. I have had 2 more water pumps after that put in. What gives? Do you know of any specific cooling system defects with this model?