I remember that a waterpump replacement was routinely done with the T-belts on a whole lot of cars

I got my 850 first and hit 70K, the "trusted indie" did the water pump too, as a matter of course

my wife got her 850 a year later and the dealer (we're now about 80 miles from the trusted indie) told us not to replace the H20 pump (and they're on the hook for a waranty) even though I asked and expected them to do it.

I'd say change it at 140K miles if you really want to change it, but given the way the dealer dealt with it, I have to go with the 850 doesn't need the change at 70K