I have three classes this year, and each one is run differently.
(TL;DR version at bottom)
Calculus: Homework is assigned for the week; due at the end of the week. Online homework due when she says it is due.
Chemistry: Homework IS NOT MANDATORY, WILL NOT BE TURNED IN, AND WILL NOT BE GRADED. However, there will be problems on quizzes, midterms, and final that are exact copies from the homework. It is in your best interest to do them.
Mythology: Readings. Readings must be done before the class day. They may or may not go over it; do them anyway.
As someone who likes to keep a tight schedule, these classes make it difficult for me to focus on what homework is a priority. If chem is never due, then I can spend the most time on it until the next lecture/chapter begins. I have a week to do homework for a math class so obviously I should spend time on that. However, I also have three to five readings due before next myth lecture so definitely have to do that.
There needs to be a balance. This week for example. I completed all my math homework therefore I am done with math. Since the topics are all review, I need very little to no time studying. Chem is difficult so I must study that, but the homework is never due so there is no rush, but I must do it before I fall behind on lectures. Myth is going to be my heaviest load. I am already behind because they ran out of the required text at the store and the library just reserved copies for the class; so tomorrow I will catch up on all required readings.
Right now, I can safely say that mythology, AT THE MOMENT, will be taking up most of my time. Chemistry and Calculus will get harder. I will have a pretty tough workload to manage.
TL;DR: Prioritize homework and study time.