Setting an expiry date to your projects is like making the photos accessible to your clients only for a limited period of time.

Soon after an expiry date is reached, that entire project or gallery automatically moves to the Closed section of your Galleries dashboard.

This will also make the share link that you have sent to your clients as inaccessible wherein they will be notified that the gallery has expired.

However, be rest assured that your photos will remain intact and won't get deleted until you manually delete a gallery.