I get from 250 to 280 shots in the hi quality jpeg mode per 512 card. As far as the battery goes I have ran it down after say two and half of these cards not using the on board flash. I have ran a battery out after a shoot then taking it to shoot for fun using the flash, seems it uses more juice than anything, using the monitor uses juice but its still not a high drain as the flash.
Hard to tell since I recharge them after a shoot whether they are fully discharged or not. Hope that helps.
BTW Its hard to hit the buffer in the jpeg mode. In RAW its not hard at all.