Preserving data is not like preserving a paining, we dont care about the
image or the form as we can change it as needed.
Magnetic media, even CDrom are viable as they do have a known life that
is adaquately long to permit copying to newer media every 10-15 years
time. The only other choices that have a better life span do so only if
they are carefully handled or more correctly not handled.
FYI: punched paper tape; MYLAR is the current long time winner... even
then it ages.
Eproms, I'd trust the newer devices longer than say the 1702 or 2708 but
the industry feels 20 years is about it. Assuming the device doesn't
fail from say lead bond failure, metalization cracking, Oxide flaws,
electromigration or other failure mechanisms common to chips. I must
point out that those failure are nearly as likely as forgetting by 20
years. Since many of those failure modes exist in all ICs even if the
eprom is good it's possible everything around could have failed.
Photographic film has shown remarkable life, it's a possible media for
many decades.
Allison