sb said:
I think shooting habits play a significant role as well.
Agreed. Mt Spokane mentioned this, too. If you fire off a lot of shots fairly quickly, you get a lot more total shots. The 500-600 shots per fully charged battery is for my personal normal usage pattern - shooting 10 shots one day, 200 the next, none for a couple of days, sometimes shooting outside in sub-zero temperatures, chimping to show pics to wife and kids, charging when I feel like it (I almost never come close to exhausting a battery), etc.
However, some time back I
tested SanDisk CF card speeds in the 7D and 5DII, taking about 1800 shots on the 7D and 750 shots on the 5DII, all as rapid-fire bursts with no focusing at all. I checked the battery stats afterwards, just for kicks - the 7D batteries were at around 70% with ~900 shots each, the 5DII's batteries were around 87% with ~375 shots each. Assuming a linear discharge rate, that translates to about
3000 shots per fully charged battery, the same batteries that with normal usage (normal for me, of course) give 500-600 shots on a charge - a 5-fold difference in number of shots for the exact same batteries, just based on usage pattern.