My wife and I have a droid each. Recently we went out of the country for 8 days. I charged both phones fully before leaving and turned full power off before boarding the flight. Both phones were turned off for the entire trip.
At the end of the trip, I turned both phones on to charge them and saw that my phone was pretty much down to 5% power where as my wife's phone had close to full charge.
Why that difference when both phones were turned off?