There were (are?) CDs and DVDs that use a gold layer rather than just silver that supposedly increases the life to something like 80 to 100 years and are still pretty cheap.
I personally still have SyQuest 270 hard drive cartridges with data that is about 20 years old, and is still there. They made up to 2Gb cartridges I believe. Don't confuse these with the junk that ZIP (IOmega?) drives used.
