No eBay APP ID défined in Kunena configurationIf powering your arduino with 6v (or 4.5v) using the onboard regulator you still have the problem that during sleep the arduino is using 330 uA. With the regulator removed and using a decent LDO voltage regulator (in my case only 4uA quiescent current with HT7333-a) you can get as low as 30 uA ( during sleeping). That's a lot less.
I'm now using one AA (1.5v) with this step-up converter:
Works perfectly. I'm not sure how long it will running on this one battery but I will keep it running and see how it goes. One advantage of these step-up modules is that the the battery will be used untill the last drop.