I've been wondering about this too. I got my mini last May 2013 and have 4 -18350's, 2 AW's and 2 Efest that are in steady rotation (I haven't noticed a difference between them). In the beginning, I used 2 per day. Now I seem to be changing them out every few hours and it's driving me nuts! I've started checking them from the charger and instead of seeing 4.2, I'm only seeing 4.0. That didn't seem terribly low, but I really don't know. I'm thinking I maybe due for some new batteries soon. I usually use a PT2 around 2.0. Doesn't AW ever do co-ops?