If we chart out a 2 tiered timeline, the upper tier being the in-universe events and the lower tier being the period in which J. K. Rowling is writing the Harry Potter books, does the lower tier ever out-pace the upper tier?
In other words, as an example, when she wrote Harry Potter and the Philosopher's Stone did she already have the events of books 2, 3, n... sketched out in a notebook somewhere?
It is an exceptionally long series, one which became wildly popular before it was complete. I am very curious how much of it she managed to write ad hoc (stretching it on and on) and when exactly she conceived the final stages of the story.