I don't think I'd want to trust tape for more than a decade or two though, as we've seen with audio tapes, iron separation from the substrate becomes an issue a lot sooner than we'd like.
Tape also has a problem shared with hard disks - to achieve high density we've rapidly hit a stage where the technology is too complex to enable data archeology at some point in the future; using 90s era complexity hard drives is about where the archeological limit is. LTO-1 may even be beyond that complexity compared to DLT, QIC or even Data8 (helical scan may be too much of a spanner in the works)
Modern polymers may make microfiche/microfilm a longer term solution than it has been in the past with acetate film/slides, but I'm not sure how much research has been done into which polymers might be best.
For longer than a century, our best experience is, thus far, with clay and paper (assuming good quality acid-free paper, rather than cheap modern consumer paper).
As someone who runs an archive for a 90s radio show, I have to contratict partly. I regulary get tapes that are 30-35 years old. The quality of those audio tapes is shockingly good. The old chrome audio tapes very rarely show signs of degradation compared with audio CDs from the same time period.
Mid to late 90s we also got the metall audio tapes that are even better. I got a few DAT tapes from the early 90s that are in same league as metall audio tapes.
Microfiche development for its own sake has mostly disappeared.
But we have a lot of great new substrates used in displays. A well produced acetate sheet may still be the best for the range of properties including aging, ink adhesion, etc. I no longer remember if microfiche is made by printing or by photo-development.
Tape also has a problem shared with hard disks - to achieve high density we've rapidly hit a stage where the technology is too complex to enable data archeology at some point in the future; using 90s era complexity hard drives is about where the archeological limit is. LTO-1 may even be beyond that complexity compared to DLT, QIC or even Data8 (helical scan may be too much of a spanner in the works)
Modern polymers may make microfiche/microfilm a longer term solution than it has been in the past with acetate film/slides, but I'm not sure how much research has been done into which polymers might be best.
For longer than a century, our best experience is, thus far, with clay and paper (assuming good quality acid-free paper, rather than cheap modern consumer paper).