I think this was already touched on, but the durability issue applies mainly to CD-Rs. These use a heat-reactive ink layer which allows a laser to burn the digital signal onto the disc. This ink can fail over time. I have a few CD-Rs I burned in 2001 that skipped enough to warrent a re-burning of them in the last year or two.
However, commercial CDs have the digital signal stamped into an aluminum layer that is sealed in plastic. Unless that plastic seal is compromised, it should last many decades, if not indefinitely. Deep scratches and high heat can warp or compromise the plastic layers, or prevent the laser from reading them properly, and are the most common reason commerically stamped CDs fail. So, as common sense would dictate, proper care and storage of your CDs is a must.
If you have a server with all of your CDs on it, and backups for that server, you should be fine for the rest of your life. When I have a CD-R go bad, I burn a fresh CD-R from my hard drive. (I use CDs in the car, and I get to every CD once in about three years, so I can flag any failing CD-Rs for replacment.) Currently, I am paying about 22 cents apiece for Taiyo-Yuden CD-Rs.