The key thing to remember is that you are practicing a mental discipline. Therefore, you need to repeat the movements (like in a dance) attentively and carefully and over an extended period of time.
It's not so much that they need to complete the worksheets as that they need to go through those dance steps (as it were).
To apply those ideas to your question:
- Students should repeat the steps on the worksheet for each lesson. They should continue to define terms for every lesson after the first. Once they have learned comparison, they should continue to compare for every following essay.
- If they find it helpful to use the worksheets to do so, they should use the worksheets. If they no longer need them because they can do the steps without the worksheet, they should do so without the worksheets.
It is true that this means the later lessons are much more time-consuming than the earlier ones. Since the first ones hardly take any time, though, we don't think that is a bad thing.
However, as students get better and better at using these tools, they can use them more efficiently. For example, students who know how to define can run anything through the steps in a matter of seconds in their heads. It's amazing how much that helps when under time constraints.
Keep in mind that you are a coach leading the students through repetitions in order to practice a skill. Once the student has muscle memory, they'll do it very rapidly.