Personally I think month is too much. I feel pretty skeptic; if people haven't had the time to even start their entries yet, how likely is it that they will do it during September either..?
I would understand the delay if there wasn't many entries to begin with, but you already have plenty and the ones who have made their entries in time (like ME for once hahaa) might get impatient and annoyed while waiting for the late ones.
I agree, I think giving a month is also too much, and also unfair to those who already did their entry in time. I'll give one week for the friends that still didn't finish the colors and things like this..