Has anyone tested how many hours of 1080p video can be recorded (not played) before the battery runs out? Is there a limit to how long one 1080p clip can be? Can I record a 2 hour long concert as one single long continuous 1080p video clip, or must I restart it continuously, say every 30 minutes? Can I record video without the screen being on? Turning off the screen should make for quite a lot more recording time, right? Any info or links would be much appreciated!