I'm also curious why you are asking this question.
Well, there are definitely personal career implications in this, but I'm also curious about the topic generally.
If for example you look at some of the canonical novelists of the past century and a half: say, Tolstoy, Dostoyevsky, Woolf, Proust, Faulkner, Nabokov, Joyce, Roth, Bellow, Atwood, McEwan and so on... these are not people who held down 40-hour+ a week jobs. Thomas Pynchon worked for 2 years for Boeing before his first novel, then quit. David Foster Wallace taught a bit. Academia/creative writing instruction/freelancing seem to be a bit more frequent, but standard 9-5 grinds seem to be rare.
Then there's another question of the differences between types of jobs. As cmi0616 pointed out above, Bukowski worked at a post office. TS Eliot worked as a banker (but his friends wanted him to quit...they worried it affected his art). Would any of them have worked as a surgeon, or done some other job that required 60-80 hour weeks -- and, even more than time, required their mental energy and occupied their mind?