If I'm bouncing or freezing a large selection of tracks then the computer will be working away for ages. So I'l go off and do something else. Check emails, browse etc. It would be nice if Pro Tools gave an audible notification when its done its work. Otherwise I won't know its done and will lose valuable time as I get distracted with something else. Ideally you would have settings so that it the notification only kicked in if the processing will take over an X amount of time.