Although as a precaution, I long ago copied them en masse to CDROMs. Later, the CDROMs got copied to hard disks.
I gave away my PDP-11 long ago, but not before I copied the 8" floppies it had (circa 1980). But one day I realized I had neglected to copy a critical file. I had the floppies, but no way to copy them. Then I remembered a friend of mine, Shal Farley, might still have an -11. Calling him up, sure enough, he had it but hadn't fired it up in years and was about to dispose of it. I mailed him the floppies.
He fired up the -11, it still worked fine, and the floppies all copied perfectly. My entire box of floppies, every byte.
A big thanks to Shal and his company, Cheshire Engineering.
(The missing file was one of the source files to Empire for the PDP-11, which I have now backed up on https://github.com/DigitalMars/Empire-for-PDP-11 )