[JimD]

I haven't checked the prices recently but after one of the guys at the local club lost his water pump (at over 100K) I looked at sources and found a huge range of prices. I also paid almost $600 for an alternator this week when I see other sources less than $300. If that sort of range is true for the water pump, I think it may make sense to buy the parts from a low cost source first, then figure out when you replace.

Replacing it before the trip is partially a function of how much of a deal it would be to be without the car for a couple days. I am not a fan of replacing parts early that may or may not fail but I'm not sure if that fits a water pump in a boosted bimmer. But I know of one that went over 100K.