The solutions for gradual forgetting and catastrophic forgetting are very different, though.

Let's consider the problem of media longevity — while, as you point out, it is not by itself sufficient to preserve knowledge, it does seem to be necessary, at least as we currently understand things. (Scholars of songlines may disagree, but of course oral traditions like songlines are even more vulnerable to catastrophic forgetting; even half a century of prohibition can obliterate them.)

If you preserve data on Flash, you need to refresh it every few years before the stored electrons leak away; standard datasheet retention times are 10–20 years, though presumably that's at 80°, so maybe you'll get a few centuries at room temperature. If you can trust in continuity of institutions, this is not a big problem; you just have an endowment sufficient to support a small number of sysadmins who make sure the SSD arrays get resilvered at the right interval, replace broken devices, etc.

But if your preservation medium has to survive the PRC nuking TSMC 18 months from now — or an invasion by a military dictatorship of genocidal religious fanatics who hunt down and kill the sysadmins and burn the archives, as happened with the Maya codices — Flash looks much less appealing (though perhaps still viable; see http://canonical.org/~kragen/eotf/ and https://dercuano.github.io/notes/atmospheric-pressure-harves...).

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I think this also bears on the question you're focusing on in the post, which as I understand it is more a question of curriculum design than of preserving physical storage media. If the target audience for the curriculum is the next generation, or three generations down the line, you can assume a lot of shared cultural background: shared celebrities, shared neologisms and modisms, shared values in a lot of ways. Hipparchos, by contrast, was writing for Ptolemaios, though he didn't know it. He died in 0120 BCE, and Ptolemaios was born in 0100 CE, 220 years later. Hipparchos was the most recent astronomer he could find to cite in the Almagest.

Amongst the civil warfare of the late Ptolemaic dynasty, none of the succeeding eleven generations had produced new astronomical observations, and the line of philosophical mentorship was broken, at least within the Hellenistic world. This bears quite directly on the problem of lost tacit knowledge you focus on in your post. Even Hipparchos was only able to do his work because he lived in Rhodos, on the periphery of the Alexandrian scientific world, which was sacked by Cassius in 043 BCE after a century of gradual reduction to servitude by Rome.

How do you design a curriculum so that it is still intelligible after eleven generations of cataclysmic cultural collapse, largely under a prescientific genocidal military dictatorship like that installed by the Roman invasion? The solution might look more like the Rosetta Project or the Cult of the Bound Variable and less like Surely You're Joking, Mr. Feynman. If Hipparchos had done a better job, maybe Ptolemaios (and consequently Colombo) wouldn't have gotten the size of the Earth so badly wrong. Maybe Ptolemaios, like Archimedes before the Romans killed him, would have followed the heliocentric model Aristarchos had developed 500 years before him (though Hipparchos did not.)