If you are using dynamic QR Codes, there is no limited scan-life and they do not expire. However, static QR Codes expire and become non-functional. When a static QR Code expires, it won’t redirect the user to a landing page or perform any action it was intended to do.
Also, dynamic QR Codes expire too. However, they can be configured to point to another URL once a campaign is over. They are editable, retrievable, and can be used for multiple purposes with no expiration. This is not possible with static QR Codes.