Hidden topics do not display on the Discussions List page, except to users with permission to see hidden forums and topics or to manage discussions. By hiding topics, you can control which topics users can access at different times throughout the course. For example, you can create weekly discussion topics for users to reflect on the material covered in each week of the course and make each topic available for one week only.
You can specify start and end dates for when a forum or topic is visible so you can set up visibility ahead of time to match your course’s calendar.
Instead of scheduling a topic to disappear as soon as you want the discussion to end, consider locking the topic at that point and keeping it visible for another few days. This allows users to review the discussion after it closes so that they don’t miss the last posts added.