Tested 1.6-41 yesterday night.
My battery drain on old versions is ~10% over night (approximately 8hrs). On 39 and 41 battery drain is reduced to only 5% over night. I think it may be that I am undervolting with titan's kernel. Also I have checked detailed power usage via powertop. There may be processes that do not take CPU cycles but keeps the device from sleeping in the deepest C4 state. For example I have this process scim-panel-gtk that would keep the CPU in C3 state for approximately 25% of the time hence reducing battery. I have to reboot every time the process is loaded (its a chinese input process and i use it occassionally).

Attached is screenshot showing the duration field.

I will keep testing to get a more consistent result on battery life and also spot any other bugs. The improvements on battery is awesome!