Hi, Which is the best media for long term storage... A DVD-R, a CD-R, USB Flash drive, good quality hard drive, tape?
Paper ironically. Next is stone (Suffers from problems relating being not very flexible), Paper is flexible and if kept inside a reasonably priced stone or lead box might survive 5 or 6 civilisations, another option is firing it off into space, no air to degrade the storage medium, it is anticipated that Voyager 1 and 2 might outlast the human species unless they bump into something first.
For us mere mortals the best form of long term storage is "refreshing your long term storage" every year or two. We are now hold patient data that goes back to the 70's, its gone from.....Punch - Magnetic Tape - Floppy Disk - Hard Disk - CD - DVDRAM - Back to Magnetic Tape and now to hard disk in two places or 3 if you count data centers backup too.
More than 1 copy is the key to long term storage, crack that and you laughing.
Ironically we had the answer all the time...Mr Caxton and Gutenberg...Make lots of copies and they survive centuries.