I think the answer is likely, "it depends." I too have a P50, and mostly leave it with the integrated Intel graphics. The Nvidia is needed for HDMI output thoug

I think the answer is likely, "it depends." I too have a P50, and mostly leave it with the integrated Intel graphics. The Nvidia is needed for HDMI output though. In any case, I do fire that up when needed, with its own X session. Battery is quite variable, but can be decent, depending on what you're doing. I use i3wm on mine, and powertop will show configuration settings that are non-optimal, as well as power-hog applications.