It’s generally accepted in the archival world that CDs and DVDs are not permanent storage solutions. As anyone who bought a Green Day CD in 1994 or pirated a copy of Independence Day via DivX format onto a DVD knows…they are a pretty unstable media and the likelihood that a CD or DVD will just stop working is very high. There are a couple of reasons for this.
First, it comes because of the way discs are constructed and written upon. Commercially made CDs/DVDs use an aluminum substrate with a dye in it. When you “burn” a disc, you are doing just that. The cd-writer heats up the dye within the aluminum to represent a 0 or 1. This doesn’t heat the disc because, as anyone who has used aluminum foil knows, aluminum doesn’t heat up much. Over time though, the dye breaks down even though the aluminum stays stable (this is irregardless of whether it is kept in light or shadow, hot temps or cold temps). Shelf life on burnt media cannot be considered safe over two years. There are now discs available, called M-discs, which were developed by the US Department of Defense. They have special writers which write *directly* onto the metal of the disc. It takes an inordinate amount of time to write a single disc, but the disc is stable for much longer (in fact, about as long as a vinyl record would last, very similar type of media).
The other reason that CDs don’t last is usually because of the way that the information is constructed. Perhaps the format of the object is old and not supported anymore. Or the self-executing program that launches the CD disintegrates due to too much copying. When archivists talk about the “best” way to keep digital media, we usually advocate for keeping everything on “spinning” hard disks–ie, a hard drive that is hooked up and plugged in. And even then, you still need to go through all your files periodically and open them, make sure they are still in working formats and haven’t suffered any “bit rot” (an unfortunate condition where the very structure of the data disintegrates as the 1s and 0s flip themselves around for no reason at all).
The main issue when we try to preserve digital materials is that we don’t understand it very well yet–digital things are 50 years old AT MOST. We understand paper, and have developed the technology over thousands of years to be stable, portable, and permanent. Digital has a long way to go before it is as trustworthy as paper, which means working harder to preserve it, for now.