Back in 1980 or so, I bought a Heathkit H11 which was a repackaged PDP-11. It had dual 8" floppy drives. I wanted it to implement my Empire game on it, which I did, and distributed a few copies of the binary. When I later got an IBM PC with 5.25" drives, I backed up the Empire source files from the H11 by writing them out to a serial port, and using a program I wrote for the PC that read from the serial port and wrote to a floppy. So far, so good.
Eventually, I put all the PDP-11 version of the source code up on my website http://www.classicempire.com./
This year, a person who had a PDP-11 emulator tried to recompile Empire from those sources, and discovered one of the files was missing! Arggh. I had long ago copied all my 5.25 floppies to CD-ROMs, but the file wasn't there, either. I had obviously overlooked backing that one up when transferring the files to the PC. I had thrown out all my paper listings, and just had some handwritten code on notepaper (I use to write code that way, later typing it in). I gave away my H11 in the 80's, but the person I gave it to had thrown it in the trash (too bad, they are valuable collector's items now).
But I did have the old 8" floppies. If only I could read them, and if only they were even readable after 27 years. I emailed my old friend from college, Shal Farley, who now runs Cheshire Engineering. He said he had an old 11 in the back room, it had an 8" drive and an ftp server on it, but he hadn't fired it up in years. I sent him the floppies, and wouldn't ya know, it worked perfectly and he imaged the floppies (about 8 of them). Every single byte read without error! I was amazed. He was kind enough to email me the contents, and I added it to the web site. I'm grateful to Shal for rescuing my data!
When I backed up my 5.25" floppies to CD about 12 years ago, about 90% copied without errors. The ones before 1985 were nearly all thoroughly unreadable, though, which is why I figured the older 8" ones would be quite useless.