It depends on the day and the week, but my pattern seems to be that I'm most productive with writing (Hubs or other similar writing) either early mornings or late evenings. The house is quiet. The lighting is right (one way or another). Whatever "real" work I have is done (or else yet to be gotten around to for that day).
With non-Hub-related stuff, when I'm on here I'm just taking a few minutes to fool around or see what shows up (in questions or the forums or someone else's Hubs), so anything non-Hub-writing related is, for me, just between-times stuff that I don't see as either "counting" or as productive. Of course, if I had a better system than I do now I could write more Hubs than I do now, but I don't so I don't. :)