The battery seems to run down in about 2-3 days on standby with no usage. Is this normal? I found the power button does not always work as expected. 1. When on, pressing it briefly turns off the screen. This means sleep mode, right? 2. When on, pressing it long leads to the pop up to choose a few options. 3. When in sleep mode, pressing the button briefly does not always turn it back on. Not sure what the delay is. Sometimes it won't come back on w/o a reboot (and once on, the battery is not zero so it's not powered off b/c of low battery) 4. When in sleep mode, pressing the button long sometime leads to a reboot. Is there some kind of settings I am missing to get consistent response? Thanks!