Yeah, I think with the setup you're intending, it's very inefficient and not practical. Basically you'll have the worst of both worlds. H.264 MPEG-4s -- possibly the best combination of small size and video quality -- are horrible for editing, so you'll end up having to reconvert them for editing in FCP. They also have no timecode, so any editing you do with them will need a time-consuming manual reconform when you get access to your online media files again.
And DVDs are not only small in storage, but they are maybe the slowest storage media available. Even the copying process is slower than a FireWire or USB drive. Even a 16GB USB flash drive would copy faster, hold more files, be more versatile (since it will allow reading
and writing) and only costs around $23 now. That's only a little bit more than four data DVDs for the same amount of storage, and files will copy much faster and be easier to access. Not to mention that a USB flash stick is a lot easier to carry around. If you're intending to edit, you'll also need someplace to store the files -- DVDs and USB flash drives don't work for this purpose. That's where Jude's suggestion of a larger bus-powered external drive comes in.
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