It took them only an instant to cut of that head, but it is unlikely that a hundred years will suffice to reproduce a singular one.
If you were a medieval scholar reading a book, you knew that there was a reasonable likelihood you'd never see that particular text again, and so a high premium was placed on remembering what you read. You couldn't just pull a book off the shelf to consult it for a quote or an idea.
You can learn many things from children. How much patience you have, for instance.

