This is the one reason I will not buy anymore flameless candles. Just too many batteries.
Having said that, I do have the larger Luminara (from Kohl's) that use 2D batteries and they seem to last a good while. Maybe 3 months on the timer.
However, I have some Luminara votives that seem to burn through AA batteries ever few weeks. I got those candles from QVC and one set went bad right away. One candle blinked with fresh batteries, so I sent back the whole set.
While I love the look of these candles, and I'm constantly tempted, I won't buy any more. I wish I had been able to get the candles that are level all the way around rather than raised on one side. They only look decent burning from the front. I see that some do not have that raised edge and I like those much better.
Oh, I use Duracell batteries, but it makes no difference at all.