iOS: For whatever reason, people love to quit apps on their iPhone in hopes of improving battery life. We've pointed out before that this doesn't work, but 9to5Mac has a supposed email from Apple's own Craig Federighi confirming it. A 9to5Mac reader shot off an email to Apple's CEO Tim Cook, asking "Do you quit your iOS multitasking apps frequently and is this necessary for battery life?" Cook didn't respond, but Federighi did, saying bluntly, "No and No. :)"
The reason is pretty simple: most apps running in the background are either not running at all or are frozen in RAM. Meaning, when they're in the background, they're not using up any battery. Force quitting an app should only be necessary when a glitch occurs. Of course, none of this is to say that apps running in the background aren't killing your battery. What's killing your battery is more likely apps with Background App Refresh, notifications or location services turned on all the time, which is why we suggest a monthly audit to clear up such things.