On days when I toiled mostly on my computer, the battery case stuck around for closer to eight hours, meaning I was almost completely done with my work day by the time the case had to come off. When it came time for our standard rundown test, the 6s lasted through 19 hours and 21 minutes of continuous video playback with the screen brightness fixed at 50 percent and WiFi connected. That still falls short of Apple's own claims, but I'm not shocked; the 6s also missed Apple's estimates when I reviewed it earlier this year.