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