Query on M9 battery
The tricky part about battery life with the m9 is that the greatest drain to the battery is simply leaving the camera on, even if it is idle and the lcd is turned off. Because it takes so long to wake from sleep, i have my camera set to never sleep. This keeps it ready to shoot, but even if you take no photos at al, just set it down and walk away, the battery will drain in 4-5 hours. if you use the camera normally, taking say 100 photos including checking results on the lcd, you can still get 4 hours out of the battery.
So a lot will depend on how you have the auto sleep fxn set up (1 min, 5 min, never) and whether you can use the camera in slow mode--ie, leave it turned off, turn it on only to take a photo, then switch it off again. If you can do that, you could get a couple of days out of it.
Use or not of the lcd is a relatively negligible factor.
Power management is one of the worst aspects of the m9, but i've found it dealable with enough spare batteries.