As we all know, on December 5, 2012 Facebook has decided to remove the
offline_access permission and has introduced a concept called
long-lived access tokens which last a maximum of 60 days.
To get Long-lived Access Token from
your own Facebook Application, This what you'll need to set up from your App Dashboard:
If you're not sure about this tool result, Use Facebook Developers Access Token Debugger to test token expiry.