I just checked and I can still read without error some 8" disks that I wrote, what, 45 years ago. They were FM 3740-type format and good quality, so there's that.
As to the value of the 8080 code that I wrote, not so much. This was only possible because I wrote the disks in a commonly-used format on a relatively common medium. Had I opted to use Memorex 651 media, it might well be gone forever. I haven't seen a 651 drive in years. Which is why I wasn't joking about using 9 track 1/2" tape. Many millions of reels of the stuff were in use right up into the 1980s. The drives are not unobtanium and the medium is pretty rugged. Had I used 7-track tape, I would still not be out of luck, but only because I have a 7 track drive, which is far less common these days. Just some food for thought. --Chuck