I edit dv projects. I keep all my source tapes. I delete from the hard disk anything that can be recaptured easily. I keep all graphics, audio, and “new” video files (files rendered from after effects etc.)
Then in Premiere I do a “Remove unused” so that in a years time, if I need to recapture my source files, I only have to recapture what was on the timeline.
Usually, doing all this gets the amount of data in the project folder small enough to back up onto a dvd.
Once on DVD, everything can be deleted from the hard drive.
bri