I’ve heard that multitasking burns more brain cycles due to switching between things, and even though you may think you are getting more done by multitasking, you really aren’t.
You know how your computer seems really fast when you get it, and then after a while it seems like it’s not quite so fast? It’s because of all that crap you add along the way. Those widget, and music scrobbling clients, and Twitter clients, and calendar agents, and notifiers, and on and on…
Video editing is resource intensive, and what I’ve found is that if I’m going to do just editing, I will log out any other users on my Mac (damn you fast user switching!) and then reboot, and then launch Activity Monitor, and quit (or force quit if necessary) any process not directly related to my task. So with a fresh reboot, and no silly little processing doing silly little things, I can go about my work. Alternately, I suppose I could create an account dedicated just to editing, and boot into that, but that’s more of a pain to me…
The reboot and quitting of processes is probably a five minute process, but saves me well over five minutes of time within an hour of editing.