If you want to stay logged in to LastPass upon browser close, leave the box unchecked. Check the box to enable this feature, and when you relaunch a web browser, you will be asked to enter your Master Password. Log out when all browsers are closed – Specify when LastPass should log out of your session upon closing all web browsers that are in session with LastPass.
As a security best practice, you can manage settings within your LastPass web browser extension Preferences to keep you logged in, or automatically log you out of your LastPass account when it is no longer in use and/or idle.
