Preventative maintenance is not a bad thing. It can save lots of grief and money. If the car is more than 6 years old and has more than 75k miles, I would change it out. Water pumps are a part that eventually wears out on any vehicle. It's much nicer to schedule the change out than have it arrive as a sudden emergency on a 3 day weekend when you want to go somewhere.
2006 M Roadster Imola Red
2000 M Roadster Imola Red (gone but not forgotten)
1997 Z3 2.8 Roadster Red (gone but not forgotten)
2008 328i Sedan Gold