Session validity time for a customer portal link created via API
The portal access URL that is generated using the portal session API is valid for 1 hour from the time of creation (in fact the API response JSON contains the expiry timestamp as well).
The access URL should be accessed by the customer within one hour from the time it was created.
Once accessed, the session is valid until the user logs out from the portal UI or logout API is called from your application for this session.
Once accessed, the access URL cannot be reused. Hence do not persist with this URL. Whenever you need to provide access to the portal, you need to create a new portal session.