> It had no problem reading all bar a handful of CDs from the mid-to-late 90s and early 00's - the failure rate was much lower than I expected.The failures were mostly completely visually identifiable too - the layers had started to separate.

It was mostly cheap CD-R from that period, and frankly you needn't wait 20 years for them to fall apart, they'd start failing under 5. Quality CD-R from good brands survived just fine.