The deadlines are much, much longer with books. When I was a reporter, a lot of times I'd come in at 8:30 a.m., get an assignment right away, interview somebody, turn the story in by 9:30, and have the finished story in the paper that landed on my desk by noon.
After I've sent my revised draft to my agent and editor, they suggest more improvement sand again, this revision phase can take anywhere from a few hours to a few months.
Sometimes I can spend as long revising a manuscript as I spent writing it in the first place.