It is certainly guesswork, but we have to try to make educated guesses.
I have media, i.e., shellac discs, that are up to 100 years old. Some brands lasted much better than others. The original owners (some of whom were relatives) are dead, the artists are dead, and some of the better material has been reissued (although is not necessarily in print), but I value being able to listen to the same discs they brought home from the store. "You can't take it with you" but can leave it for someone else to enjoy.