Lithium batteries should last a long time, as mentioned by SolRaven. Alternately, use rechargeable Nimh AAA batteries:
http://www.amazon.com/gp/product/B00...TAGHKZ57PC0PX4
(sorry for the awful link)....These do recharge (rechargers cost at least $15 but can be used for rechargeable AA batteries in all your devices), and battery life on nimh batteries is excellent. I use them in external flashes on my camera.
In fairness, lithium are probably just easier.