I don't think that's really a fair analogy, though. In 50 or 60 years, will it be as easy to recover an obsolete digital file as it is to construct or modify projection/telecine equipment to accomodate an old 65mm print today?
I have VHS tapes that I recorded on my first VCR from 1984 and they still play fine. If you're concerned about the DVD-Rs of your son degrading, maybe making back-up copies of them on VHS tape (in addition to making DVD-R copies every 5-10 years) would make sense. It certainly couldn't hurt! :)
Sorry, I should have been more clear. I understand that B&W seps have to be made in order to make DT prints, and that DT prints are too dense to yield good copies, but wouldn't a finely-tuned DT print be the best color reference for any subsequent Kodak prints made from the B&W seps? Last...
I think the general consensus is that digital restoration is fine, but there should always be a hard copy (film print) made afterwards or it won't be a true preservation (preferably a dye-transfer print to prevent color fading). Expensive, though.
That's an excellent documentary.