What's the hype with rules and deadlines? The monthly exercise is about keeping your skills sharp, getting into the habit of producing finished projects and having fun doing it. If you don't practice regularly your efficiency declines, thus point one. If you fall into the habit of seldom finishing projects you'll adopt an unconscious mental barrier that you physically can't finish projects, thus point 2. Needless to say if you don't have fun doing it you probably won't do it very well, thus point 3.
While think that a month is generally a good timeframe to work with, I wouldn't limit the quality of my game because of it. Night at Drundergond Manner took 6 weeks.
btw, did anyone ever win that?