The cold weather package does increase consumption if you are using the automatic cycle feature by pushing the slide button in on the end of the washer stalk. Every fifth time the headlamp washers run too, and they use quite a bit of fluid. During the winter, I usually go through a gallon every 5-6 weeks.

2002 X5 3.0 272,700 miles
2004 325i 118,000 miles