If you go with backups to CD's, don't forget to physically protect them. A hard case, like those cheap plastic ones, will help protect them against scratches. Scratches to the "bottom" surface are not as critical as scratches to the "top" surface, which could damage the shiny coating that your data is actually stored in because the plastic is (usually) thinner on the top surface, particularly with cheaper brands.

For long term archiving, it's best to avoid writing on the CD's, but if you do, don't use permanent markers like Sharpies, which contain chemicals that may damage the plastic over time. You can buy markers made for writing on CD's.

CD's could also be damaged by heat, so even in a safe deposit box, fire could still damage the CD's. If you keep a set at home, then use a fire safe designed for computer media. Paper burns at a much higher temperature than is safe for things like diskettes, so not all fire safes are created equal.