Life expectancy for data on CDs is 80-100 years for premium quality CDs.
Be very careful with digital storage for long-term purposes; the media itself may last a long time, but because technology moves at such a pace, the hardware to read it may not be available for as long as you might hope.
A good example of this was the BBC Domesday project in the mid 1980s, which captured a load of contemporary data (text, images, videos etc) and stored it on Laserdisc for posterity. As little as 15 years later there were concerns that, not only was it almost impossible to find working Laserdisc readers, but the file formats themselves were obsolete and couldn't be read by modern computers. Floppy disks have come and gone; CDs and DVDs seem to be on the way out, mostly being replaced by memory sticks.
The best idea I can think of is to save everything on CDs/DVDs, keep a copy somewhere online (mailing everything to a GMail account is an easy option), save it to a memory stick too, and then review every few years so that you have the option to copy everything to the next new technology before the old one disappears. Bit of a pain I'm afraid!