Session doesn't end when browser window is closed

Sorry I took so long to respond - I got hung up in a bunch of work.

I do use flash_data for all my validation error messages.

However, I checked my config.php file and I had changed $config['sess_expiration'] to 0 early in the process to solve a different issue (I even forget what that issue was). Obviously 7200 was too short then - what would be a reasonable length of time before the session expires automatically, and then I guess I should figure out where I want to manually kill the session as well.