2
When the session file is written to the USER it is clearly defined as a session cookie (which a browser automatically removes when closed).
If you install an extension that intentional prevents FF from removing the session cookies, how can you blame the system?
A easy solution if you do not want to remove that extension: click the 'Logout' button in the User Menu
// Edit: I almost forgot: you _can_ mislead the sessionsaver by writing a date in a cookie instead of session (ATTENTION: this can result in somebody being logged out while for example writing an article!). Check System Admin - Settings - Own Session.
Goodluck!
Oracle: I'd ask you to sit down, but, you're not going to anyway. And don't worry about the vase.
Neo: What vase?
[Neo turns to look for a vase, and as he does, he knocks over a vase of flowers, which shatters on the floor.]
Oracle: That vase.
Neo:...