Every individual survey can expire after a certain period of time.

In the campaign launcher click 'Security'.  

To enable TTL - simply turn the TTL to 'On'. By default it is turned off.

Using the drop down boxes set how long you want the link to remain active. Any changes are saved automatically. 

With TTL enabled, when a link is created, the TTL count down clock starts. When it reaches 0 the link will expire. It will give a notification to the user that the link has expired.

To turn TTL off simply set TTL to 'Off'