My files from the 1970's were on magtape that was written to by a long-gone drive that was way out of spec. I threw it away. My next oldest files were from 1982 or so, and were on 8" PDP-11 floppies. My 11 was discarded long ago. I contacted an old friend, and he said he still had his, though it hadn't been powered up in years. Amazingly, it powered up, and there wasn't a single bad byte on my 30 year old floppies (!). He was able to recover it all for me.
I have most of the stuff since, though floppy backups were erratic. I copied the 5.25" floppies to CD, and then to hard drives, before discarding the old computers.
I try to save most files as jpg, pdf, mp3, mp4, or plain text, figuring those are the most future proof.
Exactly! I've been mildly involved as my families archiver for years. PDF/A is the standard that the should be used for archiving docs. In fact it's what the library of congress recommends themselves for long term storage of docs. But as you said I can't think of a single app that does strict pdf/a support. I may have come across one it seems but can't remember what it was. I store everything in pdf and images as tiff.
The LOC has good guidelines for archiving all sorts of formats.
I have most of the stuff since, though floppy backups were erratic. I copied the 5.25" floppies to CD, and then to hard drives, before discarding the old computers.
I try to save most files as jpg, pdf, mp3, mp4, or plain text, figuring those are the most future proof.