As an Admin/Team Owner, you'll be notified if your team is about to expire and will have the option to extend it in the chat tab.
Here's how it's done:
Go to the Teams Manager chat window.
Select the team that's about to expire.
Click on the "Extend team" button.
Choose the desired duration from the "Select an option" field.
Enter any comments if needed.
Click the "Extend" button.
Even if you missed the extension window, you can always recover archived teams later on.
Here's how you can do that:
Go to the Teams Manager chat window.
Find the team archival notification.
Click on the "Reactivate team" button.
Select a duration.
Enter a comment if needed.
Click the "Reactivate team" button.
All notifications related to team Lifecycles can be found in the Chat tab, including Extension/Reactivation. You'll receive an email notification about these events as well.