How to Refresh LinkedIn Access Token
Unlike other social media networks, LinkedIn does not issue "Long-lived" access tokens. Long-lived access tokens are tokens which last a very long time without a user needing to re-authorize a service.
LinkedIn access tokens however usually last 60 days. Once your token is almost due to expire, the Revive Old Posts plugin will send you an email (to the admin email inside Settings->General) as well as add a message to the plugin log area about the impending expiry.
All that is required on your part is to simply click the LinkedIn button under the Accounts tab of Revive Old Posts and go through the authorization process again; just like you did the first time you connected LinkedIn.
Once that's done you'll be all set and the plugin will notify you again when the token is due to expire.