[Synchro909]

15,000 to maybe 20,000 miles is about their limit. When they get near that mileage, be VERY careful. When mine started to leak, it was the thermocouple temp sensor that saved my engine. The water leaked out till the level was low enough that the impeller was just dipping the water in the head and not circulating it. Water was not reaching the analogue temp senor in the outlet on the head so it was useless. We all know what happens if the water does not circulate. It was the thermocouple with its preset alarm going off that alerted me.
BTW All that lead me to make my own pump which looks just like the original once mounted but runs a modern ceramic seal and sealed ball races. Nothing rubs the shaft anywhere to cause wear but it involves casting a new core so it would be probably too expensive for the market.