I have some 3.5" floppy disks in the bench seat of the electric organ that came with my house that are at least that old... the three I tried worked without issue. Small sample size, but it suggests a half-life way over a couple of years; I can't imagine this system has unusually robust error correction or anything.

I recently tried to copy over an old box of floppies from the 80s and 90s. I'd say 80-90% success rate.

Floppies aren't a bad technology, but they do have limits.

I doubt that SD cards will last that long.