You've always been able to run for over 6 hours. It's just after 6 hours there's a chance you'll be force logged-off and have to reload.
After 6 hours, you may not be automatically forced off -- but if you manually log out or to the lobby, you'll have reload the client.
The six hours thing is more of a 'general rule'; it's not like right at the six-hour mark you're thrown from the game.