AA/AAA vs LiPo for bluetooth?

I've got an idea for a small sensor device that communicates via bluetooth, but I'd need to power an Arduino, the BT transmitter, and maybe an LED display for decent amounts of time (at least 3-4 hours, much more is better). With a 328p (I'd assume the 32u4 is similar) drawing 12mA and something like the RN42 bluetooth module pulling 45mA with data transfer, even if we added a ton more for slop and said the beast would pull 100 mA (when in fact we could probably pull less with a little attention to power management)... wouldn't 3 AA rechargable 1500 mAh batteries be able to keep it running (at 3.3v) for 15+ hours, or am I badly confused? Would the advantage of a LiPo pack just be size and rechargeability through USB?

(I'm leaning toward the AA/AAA side of things for simplicity but haven't done any work like that before so don't know what's involved with a power calculation like this--embarassing, really)

You have to rethink the power needs in more detail. The average current draw could be 1:100 based on how you design the stuff. For example my cheap ebay BT module draws 40/20/2mA based on actual situation, atmega 15mA/100nA, LCD display 150mA/5mA, etc..