I have 2, the 840mAh one that came with my camera and a 680mAh one that my dad gave me since he had extras for his camera. If I shoot about 100-150 per day at the highest setting, using LCD all the time, flash maybe for 10% of the shots, and taking some time to set up the shot or review it. I find that with the battery that came with the camera I can just barely get by for a day. When I know I need to conserve power I just turn off the lcd and then it seems to last forever. But yeah, an extra battery is a good idea.