You have to treat it like a computer and stay on top of what it is doing. Right after I got it I I unknowingly left a gps speedometer running and it killed my battery in hours. You'll need to download a system app that monitors and kills apps. Don't assume that because an app doesn't have an active screen that it isn't still running.
I was noticing that the GPS function in mine was impaired so I put it side by side with my other one. Sure enough, one locked on 9 satellites, the other was 0 to 4. I would think that is a hardware issue but to make sure I yanked the battery and it booted back up to full function. It seems finicky about apps and its software environment.
In other ways though it is absolutely amazing. I wonder if a pilot could give his thoughts about flying IFR with it. GPS with speed and altitude, Magnetometer (compass), accelerometer, orientation, etc.
Its like carrying 80% or more of a laptop with WAN and WIFI, camera, video camera, GPS navigation, MP3 player, LED flashlight, not to mention phone and who knows what else in one little device.