Call back in thirty years... we'll know then.

Optical media is also not stable in the long-term. Home-recordable optical media is, in fact, not very stable at all.

The only information-dense long-term storage solution we have right now is micro-film and micro-fiche, which can last hundreds of years.

With an LP, perhaps to increase signal to noise ratio, we'd record binary as audio (a la morse code) to make it unambiguous, but this would lower the data density.

We can probably do direct data recording on crystals and metal... carve books via laser into non-corroding metal tablets (gold? titanium?) and then fill the carved portions with something inert like silicon to keep the impressions free from deformation.