In Teams Manager, the duration for which a team exists is governed by the corresponding Lifecycle Policy.
If you'd like to adjust this policy, you should:
Navigate to Settings > Lifecycle management.
Find the Lifecycle policy that governs the desired team and click on it.
Click Next until you get to the Archiving section.
Adjust the Set archiving date slider to the desired position.
Click Next > Next > Update.
Your team's archival date will change to the new value you've set. However, it's important to note that other teams under this Lifecycle policy will be affected as well.
If you'd like to learn how to set up a Lifecycle policy, please refer to the corresponding article in our knowledge base.