Short of a serious fire ... or insects, mildew, mishandling by the lumpers who pack all that paper when you move, misfiling that makes the one piece of paper you need irretrievable, or about a thousand other "minor things" we've encountered. I've found paper around ten to 15 years old so brittle you needed a spatula to get a page onto a scanner to capture any record of what it said. Some "office grade" paper from about that far back doesn't last a whole lot better than that, although recent office papers, (back to about 20 or 30 years(?)) have mostly gone to "acid free" compositions that are a little better, and with them you only have the faded ink to try to pull out. (There was a certain era when many ball-point pen inks faded very rapidly, and also "smudged" a lot in storage, sometimes giving significant legibility problems.)

It really is hard to tell which is better. It's probably a little easier to keep a duplicate set of your important bits with digital stuff, but actual success with the WOM "backups" as recommended by some is limited by the hidden fact that successful RESTORES are actually rather rare.

Like the pilot who moves up from single engine to twin to have a safety margin: With two engines, you're twice as likely to have one that fails and the overload of flying a twin on one engine makes it about twice as likely that the second one will fail from the overload before you get very far.

But as the "twin engine instructor" will assure you, "you can always get to the point of impact with the remaining engine ..."

so you feel "reassured."(?)

John