If you're running a brainstorming session and have a number of people that can edit the Prezi, they will be able to log back in and make changes for up to one week. This might be okay if you want them to update it and then review the Prezi at the end of the week, but if you only want them to access it during the session you must remember to remove access once the session is finished.
Follow the given steps to remove access to your online Prezi:
Exit the Prezi canvas to go back to www.prezi.com.
Below the Prezi's preview window, click on the Edit together button.
To remove access for all, on the screen that appears, click the red Reset share links button.
To remove access for only certain individuals, click the cross to the right of their name. This is found under the Who can edit heading at the bottom of the screen.