It times out about every 30 minutes - it’s annoying, but normal.
It times out, a message comes up that says to ‘go back’ , after you do, the chat window comes back up. It may be blank when it comes back up, but if you close the window, it will reload the same chat at the same point where it timed out.
People have reported the CM told them you don’t loose your place in line when you log right back in.