Eventually, all media loses the data on it, no matter the type. Movie DVDs have a lifespan of anywhere from 50 to 300 years while recordable disks vary by type and are generally good from 20 to 100 years. Magnetic media (Floopy disks, Tapes, Hard Drives) tend to last for shorter periods, mainly due to the magnetism fading and, thus, data loss. Being that we are constantly surrounded by magnetic fields and devices that can distort magnetic media, they can't keep their data pristine forever. A few estimates I've seen range from 10 to 30 years. Of course, storing them in adverse conditions will shorten the lifespan significantly, just as storage in favorable conditions will extend it.
My advice for long-term storage: Fossilization. Lifespan: Millions to Billions of years. 😛
