This sort of question ("What kinds of hours would I be expected to work? 40/week, 50/week, more?") can be a good one to ask in an interview, both to get a sense of what the company would expect, but also to give you a sense of whether or not you'd want to work for the company. 40-50 hours, or typical full-time work is generally something you can sustain for a long time. If, on the other hand, you get an answer suggesting that they expect 80+ hours per week all the time...that suggests a culture of permanent crunch time that you might want to stay away from.