How long does a session last, and how do I log out?

Sessions persist so you are not asked to sign in every morning, and they are verified on every request rather than trusted once. Logging out is in the store switcher at the top of the sidebar, and it ends the session immediately on that device.

If you think a session is somewhere it should not be, changing your password is the blunt and effective answer: it invalidates the credential everything else is built on, and any teammate whose access you want to end can be removed in Settings and then Team.

On a shared or public computer, log out rather than closing the tab. A closed tab is not a closed session.