I can make it through a day just fine with my current phone (which I believe has a 2600 mAH battery), so I'm not too worried. I do wonder how they come up with these measurements, though. On the Nexus 6 page listing, they estimate 9.5-10 hours of Internet use, but what does that take into account? I try to optimize my phone for battery life as best I can, but if I'm browsing the Internet hardcore, my battery is almost dead after 3-ish hours. I can't imagine being able to actually keep the screen on, browsing for 9+ hours without needing to plug in to stop the battery from dying halfway through.