In iOS 4, and presumably in iOS 5, there is an easy way to completely close any apps that are running on your iOS device. Many customers complain about their device’s battery life, and running too many apps in the background can be a major culprit of shorter lifespans.
Quitting excess apps is a great way to preserve battery life, but you don’t need to always quit every app. For instance, I leave Messages, Mail, iPod and Words With Friends running pretty much all the time. I tend to close apps like Camera, Facebook and CNN when I’m done, as I only use them every couple of days.
To force quit an app, double-tap the home button (the physical button beneath your device’s screen), and the apps that you have used most recently will show up in a tray beneath the dock. Next, press and hold any app in the tray, and a red minus button will pop up next to it. Simply tap the minus sign to quit the app. If you’ve never closed out of an app, then every app you’ve ever opened will show up. It can be a tedious process to quit every app on your device, but it will save battery life. Perhaps iOS 5 will introduce a “quit all” button.
Remember, this process does not delete apps, it just quits them so they’re not running in the background and draining battery life. Next time you open an app, it will once again be added to the recently used apps in the multi-tasking tray. If you’d like to maximize your device’s battery life, consider quitting non-essential apps when you’re done with them.