Sometimes you may get error like ‘Facebook App Session Expired’ when you are in your Facebook page and it also says that you need to login again. Sessions are usually used to keep you logged in your preferred sites and services. Sessions were developed to time out so that someone else cannot get the access to your sensitive data. Facebook also uses sessions in the same way but normally reserves the sessions for third-party services and apps in order to keep your Facebook account safe. It also saves the battery life of your mobile phone.