40 years indicates you're probably using 5¼" (or larger!) media which is slightly better at media decay due to lower densities.

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 )

Overwhelming majority of the disks were readable. I have about 15-20 that aren't... and many of them may be formatted Mac 800k which I am not able to read out right now, rather than corrupted.

This even includes many DD disks that were formatted as HD by my PS/2 that just didn't care. Was a slight hassle to get newer drives to ignore the absence of the density hole and read them out.

The bigger problem is that almost all the interesting data I'd want from that era was generally overwritten by dumb stuff. Why keep old papers and source code from when I was a "baby", when a friend was offering a copy of a game?

Maybe consumer floppies were of a lower quality than published ones? I don’t know if that’s true but I do remember having a really low success rate with consumer floppies (it got so bad I’d often write two floppies just in case).

I think stray magnetic fields were more of a problem back then. Fridge magnets, magnetic clasps on wallets and bags, magnetic clasps on notebooks and binders, etc. There were lots of hidden opportunities for corruption.

These days, nobody worries about the mag stripe on their credit card getting wiped. But it was an active concern back then.

I'm more annoyed when a store doesn't take Apple Pay. The clerks always seem embarrassed when I ask because I'm sure I'm the 900,000th person to inquire. I find it so odd that the Krogers in two cities I've been to recently don't do contactless payments at all.

I do remember cassettes had different quality magnetic strips but I don’t know if the same was ever true for disks too… so it’s probably bonkers. I’m just throwing some ideas around without much thought. :)

It might just be a case that college kid me was less careful with his disks than you were.

More recently though, I have unboxed my old collection of 3” (not 3.5” but literally 3 inch) floppies for the Amstrad CPC 464 and they almost all worked despite being nearly 40 years old. So I definitely believe you when you post about your success rate.