Reviews of the E-M10 spec the battery life at just over 300 shots and many recommend carrying spares if going out for the day. I've read similar things about my Fuji X10. I have done a number of shoots on both cameras in medium burst mode and come home with over 600 photos taken over a period of a few hours. Yet the battery meters on both cameras still show full bars. Have I managed to circumvent the laws of physics or am I just not taxing the camera enough? Just trying to understand if I should invest in extra batteries and how many.