I've come up with a new art challenge I call '103013'. On a given day I allot myself 10 minutes to draw something, then I make a second version in 30 minutes on a slightly larger canvas, then another in 1 hour on a yet larget canvas, and a final one in 3 hours  (or as long as it takes me) of the largest size. While doing this I noticed that with each iteration I was able to see more clearly what was important about my subject, and so I was able to accomplish much more in comparably less time. This was my first attempt (of course I begin with the obligatory skull study), and the results make me think I'm on to something. Please let me know what you think or if you try this.