Need Help in Expiration of access Token in FB API?

You don't have to authorize the app more than once, it's just that your app is going to have negotiate a new access_token when it expires. This is done using the cookie and a "code" which is in that cookie as long as the user is logged into facebook. I suggest reading this documentation very closely as it outlines how you do the "oauth dance" to create access tokens either client or server side.

Make sure that ‘Deprecate offline access’ is enabled for your app.

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