You are not being annoying Deborah, you are showing your students that you care about their success (although I agree that some of them may think it is annoying :-)).
I would also encourage you to set deadlines for your students and make it clear they cannot turn in assignments late unless there is mitigating circumstances that they have talked to you about. I have found that to be very helpful in getting the students to stay on task. Putting it off until the very end of the class is never good for the student or the teacher!
