As has already been commented on in many places, Steph Swainston is stepping down from full-time writing in order to become a Chemistry teacher and, presumably, to suffer the sullen stares and unspoken death threats of every English teacher/frustrated novelist she encounters from now until the end of time.
I was a little surprised when I read the article because to me, a full-time writer taking a step back from what can for some be a gruelling schedule isn't really news. And she doesn't even say she's intending to give up writing; she wants to go back to working at her own pace, which seems to me to make the article even less genuinely newsworthy. Even so, one can only wish her luck.
Personally, I'm on a steady, one book a year schedule, at least so far. Sometimes that can get a bit aggressive when I get close to a deadline, but having just come out of some very, very long days of writing over the past few weeks, I feel pretty good about it. Some writers write well under pressure, some don't. I'm one of those who do. The real question, of course, is can one write well to a deadline, or does a book automatically become better if it's been laboured over for a long time?
Sometimes you meet people who aren't writers, and find they've picked up the idea that 'great' books are by necessity languished over for years, forgetting that many famous authors wrote at speed, and often to commercial requirements. But then again, there are plenty of successful authors who really do work best at a much slower pace. So, to answer my own question: How long should a book take to write?
As long as it takes to write it.