I'm pretty happy with the battery life so far. I was seeing ~18 days per battery with my current application. Since the firmware was around the 10th, I'd have gone through a complete battery replacement since then. Coincidentally, it was right around the 10th that I did replace all the batteries anyway. At any rate, all the voltage levels are hovering around 2.8-2.9, which is great.
I made this little excel plot of one of the voltages over time just to see the "before fixed firmware & after" difference..
I made the "Fixed" graph start on a battery replacement, but I think the little upward jog in the line around 1/10/17 is when I updated the firmware.