Hi,
CDs aren't a great long term storage medium. IIRC they are rated for failures between 6-10 years, but that of course depends how you store them (e.g. humidity, light, vertical or horizontal, the kind of packaging they are in, etc. etc.) and the quality of the blank disc itself (always buy good brand name disks).
I've had backup discs that failed after a few years, while others have lasted over 10 years. It's a lottery really. Not ideal for storing important and valued images.
If you need longer term archival storage I would recommend one or all of these (in order of reliability, lowest first):
1. Have multiple copies of each CD / DVD. If one fails to read, at least you can try the other one. Blank CDs / DVDs cost pennies these days.
2. A second hard disk inside of your PC - use it to keep a backup copy of your images. Your main image folder would of course be on the first hard disk. Two hard disks lowers the chance of data loss in the event of a failure.
3. An external hard disk - same as 1, but a fault on your computer is less likely to impact an external drive (e.g. power supply failure). An external drive must have its own power supply.
4. Two or more external hard drives for generational backups. More drives = less chance of data loss
5. Use off-site storage - Always keep one of your external hard drives at a different physical location, say with a friend or relative. If your house burnt down, or you were robbed, could you guarantee at least one of your backup copies would survive?
6. Online storage. Lots of ISPs are offering this service now. You can get 30Gb of online storage for about £20 GBP a month, and in the USA for a lot less. An ISP will have lots of redundant hardware, duplication, a second tier backup etc. Your data will be safer with them than on your home computer. You just FTP the files up and they do the rest.
Also, consider investing in decent back up software to automate backing up your data.
I use Syncback (
http://www.2brightsparks.com/syncback/syncback-hub.html) but there are lots of good solutions out there.
Hope that helps.
Cheers
D.