Well, it depends on how much time you have to put into each day. The more maps you make, the much easier it gets, and the less time it takes to push out something of acceptable quality, believe me.
So far the deadline is still the 20th of this month, but I see many people in his contest thread asking for time extentions. I suspect he'll probably grant them.
I will still be posting my stuff on the 20th, though. By that time I'll have been waiting to post my stuff for 3 weeks.