I was talking to a friend of mine who teaches four courses a semester at a local college. She treats her job as a 9-5 one, putting all instruction, preparation, and grading - along with committee work and other service - into 40 hours a week. Then her own writing, of which there is a lot, gets done outside those 40 hours- weekends, evenings, summers.
I teach 2 courses a semester, so I could do all my teaching and service in 40 hours a week and still have time to write and do research during the actual work week. Yes, I could be one of those people who brag about how many hours they work, but I'm not that guy. An hour of work for me can be extremely efficient and productive and I'd rather work 30 good hours than 60 mediocre ones.