This is also a handy add on for a new sites.
Keep user online for n number of minutes after user logged off (session ends) from the site. n could be few minutes to day or so (0 - 2000 minutes) before status change to when was the user last online. May be we can mark this period as 'Away'.
This gives the newly logged in user feeling that site is busy and encourage them to chat with 'online' users.
Also if we can activate this feature gender base, its even better.
My site Urban
Population 1000+ 9:1 male female ratio