Greek literature exists due to recurrent utility, not material preservation
Do we know why so much of Xenophon survived? I can well imagine Plato's sect perpetuating his writings and others beyond as he became *the* reference for the emergence of philosophy. Much of Aristotle's work is lost and what we have allegedly survived in a barrel and later reemerged. But why so much Xenophon? (Not that I am complaining.)
"in perfect conditions their microfilm can last up to 500 years"
Perhaps quartz will provide a more durable "window" into the past. In one advanced application, quartz can preserve info in "five-dimensional data storage", with data density about 10,000 times greater than that of a Blu-Ray disc. Even at such extreme density, the data is secure within the quartz disc for billions of years.
One such disc was placed in the glove compartment of Elon Musk's Tesla Roadster, prior to the car's interplanetary launch aboard the first Falcon Heavy. The disc contains Isaac Asimov's Foundation trilogy, plus instructions for decoding.
“the rotten tree-trunk, until the very moment when the storm-blast breaks it in two, has all the appearance of might it ever had.”
― Isaac Asimov, Foundation
Hypothetically, if you could fill a disc to its 360 TB capacity and secure copies wherever needed, how might you structure that disc's content to enable a fast and successful "civilization bootstrap"?