So why doesn't that apply to the timing belt?
You get the timing belt changed when it's working fine as preventive maintenance, before it breaks. The same principle applies to the water pump 'cuz it's so difficult to get to. You have to dig deep to get to the water pump behind the timing belt. As long as you're right there anyway, it'll take just a few minutes and not much money to change the water pump.
If your water pump fails soon, it'll be such a waste to have to remove the timing belt again. You may say, "the water pump will probably last for years longer". You could say the same thing about the original timing belt. If you decide to do preventive maintenance on one part, why neglect the other?
A broken timing belt is rare. A water pump problem is much more common. The water pump is by far the weaker part. If you're only gonna change one of those parts and not the other, I'd change the water pump. Change 'em both and be done with it.
Mark Griffin