Funny responses. Having been a composer, I (and I hope, my batteries) prefer Joh Cage and Vladimir Ussachevsky.
I bought my second battery and will not worry about extended life. Since I shoot lots of 6-frames-per-second bursts, I will switch batteries when the first one cause a significant slowdown (about 50% charge, according to the camera's report,) and recharge both when I get home. My life is too short to have to spend more time worrying about a few weeks, either way, on a $60 battery.