I wish I had an answer for that, mine works great all day (or until I use up the battery) especially as compared with my 510 - I could always tell when it was about to die because the vapor dropped off, with my eGo I can't tell until the light starts flashing.
Same for me, although I've only had that happen once since I got mine. Pushed the button, started a drag and *blink, blink, blink*....dead. Thank the PV gods for extra batts!