Distinguish or isolate the intro and conclusion about the Nonlinear Library from the main content.
Ideally, use a different voice (eg, a human recording). A common solution is to insert a chime. Either of those would require splicing audio files. If you want to keep to just splicing text files, maybe there's a way of inserting something to make the TTL pause?
It may be hard to compare art from different periods, but it is direct to compare science and engineering from different periods because the same thing was discovered or invented multiple times.
Knowledge is not a ratchet. Sometimes knowledge is lost. But it is not only catastrophes like burning libraries and riots against scholars. There are Leaden Ages where scientific knowledge is lost century after century, such as Alexandria for about five centuries starting 150AD. Any period of progress is a Golden Age compared to that. Do people know that they are in a Leaden Age? I don't think the Alexandrians knew. The first task is not to fool yourself.
If a second age reconstructs the knowledge of the first age faster, it might be because they are better, or it might be because they are supported by the notes of the pioneers. But what if they are slower? This is strong evidence that the first age really was Golden. In particular, the Hellenistic Age, 330-130BC, subsumed virtually all scientific progress for thousands of years, at least to 1600, and maybe to 1700.