When CDs and then DVDs were invented there was this view that data burned to and stored on recordable optical media would just about “last forever”. Turns out that this is far from the truth. The reality is that data burnt to recordable optical storage media starts to decay almost immediately; in the very first week. This is known as bit-rot. However the massive data redundancy and error checking and correction that is employed in optical storage technology means that even so you can still (usually) read your information years later despite the occurrence of bit-rot.
The question is, how many years later before there is too much bit-rot you can’t read what you burnt to that recordable optical disk?
Based on a recent TWiT episode featuring John C. Dvorak it seems you might be risking your data if you trust it to recordable optical storage for anything longer than 10 years.
While it depends on the quality of the recordable media used (not all CD and DVD optical media is created equal), the specifications of the burning unit used, and the speed of the authoring burn, the view is that for about 80 percent of CDs and DVDs created using ‘domestic’ recordable media and burners the bit-rot after 10 years will exceed the redundancy and error correction capabilities of the technology. Which means—you won’t be able to read everything on the disks! And if the ‘hard’ errors are occurring in the index areas of the optical disk then you may not be able to get anything off it.
Fortunately this 10 year data degradation problem does not apply to pressed optical media so you can expect your retail purchased music CDs and DVD videos to last much longer. They will most likely still be readable (playable) well over 100 years from now providing the clear lens surface is not scratched or otherwise damaged.
So, the bottom line here is: If you have anything important stored on recordable optical media that you authored about 10 years ago or more then now would be the time to do something about it. Either copy it back to your home SAN server or NAS server (which you are backing up to an external 2GB USB drive), or duplicate it onto fresh recordable optical media so you can store it away for another 10 years or so.