One really can't say how long either will last. Both in theory shoudl be good for at least 150k miles or more. Sometimes they last and sometimes they don't. My waterpump housing went at 65k miles. My alternator still runs liek a champ. I've only got 80k miles on my car thoguh, so I can't really tell you much omre than what I've experienced. I haven't heard of the Alternators going on these cars, so it should last quite a while. As far as the water pump goes, it's usually athe gasket around the housing that fails. When that goes, you might as well just replace the pump seeing that it has to come apart to do the gasket and what not.