Rap said a few posts back:

Believe it or not, magnetized tape can erase itself over time. Here comes the interesting part: preservationists are finding the CDs can also! Vinyl, glass, wax, and similar recordings do not.

The questionable part is "Vinyl, glass, wax, and similar recordings do not."

Especially vinyl and wax are "worn" each time information is read from them by the common methods. Archivists have found methods of "optical reading" to minimize the wear, but the remaining critical factor is that there are no materials you can make a recording on that don't spontaneously change dimensions even if left undisturbed in "perfect" storage conditions. This effect is most evident where physical/mechanical dimensions of the medium are where the signals are stored, as with vinyl or wax.

I have a copy of a report from a study done a few decades back on a group of carefully prepared samples of "the most stable materials available," carefully prepared to be "defect free" and very accurately measured before storage in "perfect conditions." The materials tested were ones selected for their better stability for use in making very high precision navigation instruments. Every sample showed easily measurable changes in dimensions after storage for only one year. And the "perfectly made and stored" platinum "meter standard bars" were discarded as references for the standard some years ago because they kept changing lengths.

The older media that many people say last longer are most often those used for analog recording, and small changes are less easily detected in an analog signal. Hence the general agreement that those old records "sound better" when played a few decades later. You cannot determine whether they still sound exactly the same as when they were made, and there is pretty good evidence (and even more opinion) that most of them actually do sound at least "a little different" after every few decades. Any one with much experience with the old recordings will generally agree that they sound different after "many playings," and "wear out" if played too many times.

This isn't an argument that they don't "sound better." It's the little question of whether they sound the same forever that nags.

John