I assume that absolutely any electronic storage device has an innate
capability to change itself to junk in the blink of an eye, so adopt
nature's normal low-tech solution to this type of problem and simply
scatter copies of files all over the place on the grounds that some
will survive somewhere.  Those that do can themselves be scattered
in turn.

The data format -- MIDI, bespoke roll-master form, list of events
in ASCII text or word processor form, whatever -- is quite irrelevant,
as it's the data content that's being preserved. If it matters enough
to anyone in the future they'll figure out how to read it!

However, when searching for paper to use in my piano roll perforator,
I located Oce photocopiers' "Red label" paper, available off the shelf
in rolls 200m long and 297mm wide, ideal for low-volume production.
It has a claimed durability of 150 years, arrived at by some form of
accelerated aging process, I assume. Whether this is real or illusory,
at least the paper's life has been considered by the makers, which
I'm sure is more than was done for original roll paper. It's slightly
thicker and springier than earlier paper, but tough to go with it,
which also ought to prolong its usable life.

So, using the recently-acquired ability to produce replica roll masters
and thus proper replica rolls, new rolls ought to be around for a fair
while and be adequate for a future enthusiast to replicate again should
any instrument still be functional at the time. I reckon that
well-produced rolls will outlive their electronic masters by at least
a century.

Julian Dyer