“Digital preservation is really just an oxymoron at this point,” says Jan-Christopher Horak, director of the UCLA Film and Television Archive. “It’s really just putting plus and minus electronic charges on plastic — and that plastic has an extremely short half-life. So that most digital media, even if you take it and store it correctly, is probably not going to last more than eight or ten, maybe 15 years.” By contrast, with 35mm film, “we just need to put it into a cold, dark, dry place, pay the electricity bill, and it will last for 500 to a thousand years.”
In one of the most famous examples of the perils of digital preservation, when the makers of Toy Story attempted to put their film out on DVD a few years after its release, they discovered that much of the original digital files of the film — as much as a fifth — had been corrupted. They wound up having to use a film print for the DVD.
From Bilge Ebiri, there is more here.