My iPhone 6 128GB seems to last all day long without need for charger. You definitely need to pay attention to how many things your device is doing, however. If you have turned on wifi, bluetooth, GPS, etc., or you like to stream YouTube videos all day, you will use up your battery much faster. If you are in a remote area, your phone will actively search for a signal and that uses more juice than when you are in a strong signal area. Wifi can also be a battery suck -- esp if it is a poor connection. And lastly, the 4G bands are known for the way they can cause devices to use up power. This is why all the new devices let you "switch off" 4G and restrict to 3G or lower if you don't need the higher speeds. Playing music, interestingly, barely seems to touch the battery at all -- I listen to music quite a lot and have always been pleasantly surprised to look hours later to see that the battery meter has barely moved. If you travel -- you really should invest in one of those "booster" batteries that you can plug your iPhone (and iPad) into to charge while away from your office or hotel. But I can almost always get most, if not all, of a full day without worrying too much -- just remember to shut off stuff you aren't using at all (like shutting off lights in rooms you're not in....)