It's set and enforced by the system itself, so you'll see that if you try to submit something for official critique right now, it won't let you. This is for several reasons - I don't want to encourage students to get a bunch of work done ahead of time, then submit it all rapid-fire (which would overwhelm me and my staff), and I also don't want students to rush to get everything done as quickly as possible, submitting work that isn't their best instead of taking their time to ensure our feedback is as relevant as possible to where their skills and understanding are presently.