This is not just a Crossfire issue, it is across the board on the newer cars with more computerized systems. My new 07 Mustang GT/CS lasts about 5 days. This is an issue that has been continually raised on the Mustang Forums. Ford has a "High Electrical Content" battery, for cars equipped with all the "toys", but my Mustang has the standard battery, although it has all the toys, including the active alarm system.

I never experienced this problem with the Crossfire, but I was in Dallas, at the time, and the car was driven every day. I did leave it in the garage once for four weeks, but it was unlocked, with the alarm off. No problems when I came home.

I purchased a battery manager, for the Mustang, from Griots Garage (Battery Manager III - $79.99). However, there are much cheaper ones out there. I have had no problems, even in below zero weather of South Dakota, since plugging it up. I only drive on clear, snow & slush free days, so she spends a lot of time parked. Keeps the battery fully charged, at all times.

Here is the address: http://www.griotsgarage.com/