Pro and Powerhouse users can set an expiration of the entire feed. At that time, the feed disappears for listeners and content is inaccessible.
On a Specific Date
In the Feed Properties, select "On specific date" and the choose your date and time. The timezone is the system timezone of your computer.
At that time, all listeners will lose access to the feed and its content.
Days after Listener Start Date
Select "Per-listener days after individual listener's start date" to have the feed expire after a specific amount of time for that listener.
For example, this is useful if you have a 6-month program with ongoing enrollment. You can set the feed to expire for each listener 180 days after they're added to the feed.