I have a DM42 (which I absolutely love) and to be honest I'm a bit disappointed in battery life. I think it lasts a few weeks at best, and I know the battery is almost done when it starts resetting to the splash screen with a beep when I turn it on. The easy workaround for me, since it basically stays on my desk all the time, is to leave it plugged into a USP port. I noticed another comment saying the battery life is excellent so maybe mine has an issue, or my custom SI units program/menu sucks down the battery life!