Which would you rather do? Get 8 hours of sleep everyday, or exercise 5 hours a week?
There's a lot of literature that workouts beyond an hour-hour and a half don't add much benefits and the shorter and more intense they are, the better. (of course this does not apply to athletes)
I've also found that, by bike commuting, I can integrate exercise into my day in a way that doesn't really take much additional time.