[0X1A]

I have this exact machine with an i7 and do not get anywhere as low as 2 hours. Do you have bumblebee installed? It sounds like you might have the dedicated graphics runnign at all times, which is the case if you don't have e bumblebee + bbswitch installed.

[dnlrn]

This depends on the distribution. Fedora for example has GPU switching using PRIME working fairly well and automatically disabled the dGPU by default.

[0X1A]

Wasn't aware of that, though the current performance of nouveau is pretty horrendous. At least for newer cards. It's a bit unfortunate but to essentially have a working card you must have the proprietary drivers installed.