Using the new endpoint below,you will be able to extend the
expiration time of an existing,non-expired,short-lived user
access_token. Please note,the endpoint can only be used to extend
the short-lived user access_tokens. If you pass an access_token that
had a long-lived expiration time,the endpoint will simply pass that
same access_token back to you without altering or extending the
expiration time.

To get the long-lived user access_token simply pass your own client_id
(your app_id),your app_secret,and the non-expired,short-lived
access_token to the endpoint below. You will be returned a new
long-lived user access_token; this access_token will exist in addition
to the short-lived access_token that was passed into the endpoint.
If you would like to refresh a still valid long-lived access_token,you will have to get a new short-lived user access_token first and then call the same endpoint below. The returned access_token will have a fresh long-lived expiration time,however,the access_token itself may or may not be the same as the prevIoUsly granted long-lived access_token.