You can set an expiration date when all the files in a team will be deleted.

Right click on a team and pick "Set Expiration Date" pick a date, press "save" and the files will be deleted at midnight (23:59) at the chosen date

A team that has an expiration date will have a clock by the team name. A banner is also shown when the team is selected.

To remove an expiration date, you open the same dialog again and click on the small x to the right in the highlighted date.