Most of the time historians use the phrase 'Dark Ages', nowadays, they mean the time from roughly the mid-sixth century to about Charles Martel, where there are only a handful of written and architectural records remaining, almost all from the margins of Europe. His examples are mainly before or after that time period. But even accepting his much more broad time period - and one of his examples is more than 100 years…
There's probably more records remaining than we realize because of the rampant recycling of old parchment.
AFAIK the 'Dark Ages' refer to our lack of records only, and the rest is misunderstanding.