Here's what we know:
* He was known for his quick writing style: Some of his books, like "Charlie and the Chocolate Factory," were written relatively quickly, over a few months.
* He also had periods of writer's block: This is often the case for many authors. Sometimes he would struggle with a particular story for years, or even abandon it entirely.
* He was a meticulous editor: Even if a book was written quickly, he often revised and rewrote it extensively, which could add months to the overall process.
Ultimately, the time it took Roald Dahl to write a book depended on many factors. There's no hard and fast rule!