Generate Page Access Token (Never Expire)
Note: You need to have admin access to the page first
Go to Graph API Tool: https://developers.facebook.com/tools/explorer
Set the Facebook App and ensure you choose a Page access token, select permissions shown in screenshot
Click the blue “i“ icon → Open in Access Token Tool
Notice the expiry date is only about 2 hours (short lived token). Press the “Extend Access Token“ button at the bottom of the page
Copy the new token, this one should not expire