Marinel Sigue/BGR Nothing ruins a reading session more than your Kindle dying right when the story is getting good. While this e-reader is designed with an impressive runtime lasting anywhere from a couple of days up to six weeks on a single charge, it still needs charging eventually. But what if you're traveling and nowhere near an outlet? Or if you want to settle into a long stretch of reading without getting interrupted? There's one Kindle setting you should change to get the most out of its battery: Airplane Mode. It turns off your Kindle's wireless connections, so your device isn't constantly sending and receiving signals that can deplete the battery. In turn, you won't be able to get new books, sync your library, or use Kindle features like Wikipedia and Translate. However, since your books are stored locally, Airplane Mode has no direct effect on the reading experience itself. You'll still have full access to your library, all while enjoying a longer runtime.…