If you're using iMovie, just do your best to capture, edit, archive to digital tape (miniDV or Digital 8 probably for you) or archive to DVD and then erase it all and move on to your next project.
I'm going to make the assumption that you are editing for TV playback, like family videos or personal projects, etc.
Doing some quick math, it looks like you have captured around 3.5 hours of footage. I don't know what your specific project is, but if you've captured everything you need, just finish your poject, dump it back to tape, erase your files (backing up your project files) and move on. Does iMovie let you recapture from a project file based on timecode? I didn't think the early versions did.
Don't even think about transcoding with iMovie. iMovie isn't sophisticated enough to go there. Also, PLEASE don't resize, crop or otherwise try to manipulate your footage to save disk space. It's just going to look like crap and get you nowhere.
Final Cut is a much preferred solution, because you can log your clips before you capture, so you can get very specific and just capture exactly what you need. I don't use iMovie, but from what I recall in playing around with it, you're forced to capture on the fly or capture the whole tape at once, wasting disk space.
Additionally, FCP lets you capture in low res mode (1/10th the space) and recapture later using timecode references at high res.
Your best bet is to be very disciplined in what you capture. Only capture what you need, edit it, back it up, erase and repeat.
