I set 11:30pm deadlines for assignments in my e-Learning course because I want to respect that students work on their courses at times outside of the instructional day. Some students take online courses specifically because of the flexibility of learning anytime, anywhere.
But most students behave like temporal gases: they will fill whatever container of time you put them in. So a side effect of that graciously long submission window is that students who could finish their assignment during the school day don’t, and they all try to cram it into their evening instead. Then they stay up far too late, which is bad for a ton of reasons.
So setting an 11:30pm deadline might have been a mistake. In the future I might set it for 3:00pm and simply expect that some folks will be a little late. At least the punctual kids will get to bed on time.