Dan Brown & The Lost Symbol: wrote 7 days a week starting 4 a.m.

According to this interview, Dan Brown took six years to write The Lost Symbol because he was determined not to write a "lame follow-up" to The Da Vinci Code.
He wrote seven days a week, starting at 4 a.m., including Christmas. Dan Brown: "I've probably written 10 novels worth of pages to write The Lost Symbol."
Dan [...:]