What is the problem with EPROMs? Why not just put them in styrofoam?
That should keep IR out...
And wrap them in aluminum foil to keep out the beta radiation, or even
better lead bricks, keeps out cosmic rays and background radiation, oh,
and move to some place with low radioactivity in the soil (hmmm, lets me
out, Nevada is one of the most heavily nuked areas in the world), and
store them at some location with a low altitude too, say the Dead Sea or
Death Valley. I almost forgot, are the ROMs ceramic? Bad news,
transfer them to plastic OTPs, ceramics generally have materials that
source beta radiation. Those pretty white and gold cases could be
destroying bits even now.
Seriously, I preserve ROMs in the S-100 boards by disassembling them and
saving the source code. I have about 30 backup tape generations on 4mm
(I do one at the end of each month, well, 2 now, bigger disks), plus
older backups on DC600 cartridges, and an offsite backup too, so I don't
worry too much about losing them. And an extra advantage in having the
source code is you can actually figure out how the hardware works, not
have to depend on the skimpy manuals. The only drawback is that it is
time consuming.
Jack Peacock