For security and compliance reasons TalentLink must provide support to ensure that should a user walk away from their device and forgot to logout of TalentLink / close the application window - thereby possibly leaving candidate personal data visible on the device screen - TalentLink "protects itself" by ending that user-session automatically on their behalf.
The current time out of 30 minute.
This is also the case for any forms sent to external users (e.g. referees) the form will only remain active for 30 minutes, after which if the user tries to submit it will fail and they will need to close the window and re-access the link to start again.