I use a K-7, with the original Pentax battery and the original Pentax battery charger.
In the K-7, I switch off (completely) the LCD screen, I kill off all in-camera PP (for a number of reasons other than battery life) and I rareful use the flash.
I can get easily 850 shots with still some juice in the camera. As a principle, I never ever discharge completely the battery: I had some nasty experience wth other cameras.
With a genuine K-7 Pentax battery, the life is linked with the number of options requring LCD screen, in-camera PP, flash .... The battery icon is not very accurate. When it starts to drop, you can still do a few hundreds of shots.
Hope that the comments will help...