When it comes to homework, I would recommend doing it right after the class if you have the chance because the information is still fresh in your mind from the lesson. Also remember to use your notes to help you with you homework (unless the assignment states otherwise) because that can really improve the accuracy of the work.

When it comes to Extra Credit work, I would say to do it if you have the time because it can help your future essay work and your long answers, plus you get house points!