I've never read Lisa's book, but the Autosave feature of FCE will do the same thing; make backups of your project file as whatever time interval you want. It's a good idea to store the project files and the Autosave Vault of different hard drives in case one goes bad.
Of course, you can also make backups of your project files yourself by using any number of available backupp apps, including Time Machine.
But I think she may have been referring to cases when you want to make revisions, yet save the old version just in case you need to go back. The Autosave Vault will do that, but you can always go to File->Save As and then save using an appended name such as "My Project v2" or "My Project 040112" (if you want to include the date).
Normally, I don't create a new project file to do that, I just duplicate the Sequence and then give that Sequence a name indicating which version it is. That way all versions are within the same project file.
-DH