I didn’t think it’d live up to expectations, but it did.
6-cell battery. Windows Power Manager. Second to lowest brightness, WiFi on. Idle and load-free though.
This is almost how manufacturers do it. Their screen is usually on the lowest brightness setting, WiFi switched on or off, and some simplistic blank browser running. The screen might even be closed in some cases.
Further real-world testing:
I must’ve spent over an hour posting something on a forum. Battery started at about 95% or 93%, can’t remember the exact number. Close to 6 hours at that percentage (5:55 range). After an hour, the battery draimed to about 77% and still had about 5 hours left (4:54). Pretty impressive.
WiFi on, Firefox with several tabs, screen a few levels brighter than the screenshot.