Each module or lesson will require you to some sort of activity. The activities are designed to provide an opportunity for you to either apply what you are learning or to look more deeply into the concept about which you are learning.
As a responsible adult learner, you are expected to complete the activities assigned within the timeframe allotted. You are typically given one week to complete the activity and any other assignment for that module, lesson or unit. Very few instructors will grant extensions for assignments. They simply don't have the time it takes to keep track of late assignments.
If there are reading assignments posted, it is expected that you do the reading in a timely fashion, as well. Some learners try to complete the discussions without doing the reading, and quite frankly, it shows. Learners who read their assignments prior to responding to the discussions tend to provide much more insightful comments than those who do not do the readings.
What am I trying to say here? Do all of the homework and assignments each week!