My brand new M3 lost 30% of charge (from 300mi to 200mi) after being unplugged in my garage for 72 hours. Sentry mode was the only possible culprit. Going to disable Sentry while parked at home and re-test. If validated, it would suggest using Sentry mode a bad idea if leaving car at airport parking for more than 8 days (assuming zero miles left after 9 days.) Note: Sentry mode being active was also inside a closed garage with the only "stimuli" being the blinking green LED on my furnace controller.