It's not complicated unless some makes it so, or gets the occasional bad application or bad device. I do battery testing of both Android and iOS devices, so don't even pretend it does not happen to iPhones. It is a more controlled environment, but it still happens on occasion. My wife pulled her HTC out of the box and has been using it for over a year. Her phone has never run out of power in less than a day, and she usually end up with more than 50% at bedtime. She's a big music and YouTube user as well, in addition to having wifi, Bluetooth, 4G LTE data, and GPS on 24/7. This is her first non-Apple phone, and she's lovin it. The other aspect is that Apple intentionally skews the battery percent display to give the users a perception of better battery life. This is why Apple does not allow any apps that display the actual battery voltage.