At the Nov 09 monthly meeting, I was asked about a scratch disk dilemma.
Problem: Shooting four on-going projects that will take a long time to finish shooting and editing. More footage than will fit on a 1TB drive. PITA to keep resetting the scratch drive all the time.
Solution 1: If you look at your FCP System Preferences (Final Cut Pro > System Preference > Scratch Disks), you'll notice that you can designate more than one scratch disks at a time. When the first one fills up, FCP will move to the next one. So set multiple scratch drives at one time. See the graphic I attached to this post.