But do you think you did so well early in the term as a result of the deadlines? Perhaps it had no impact, but I'd argue that a lot of people need that requirement to stay on track.
I found that it worked both ways. When I started, the deadlines kept me motivated. But when real life intruded, and I had to take a break for several weeks, that fact that I was behind was a demotivator. A good middle ground might be "unlocking" the classes - there is a two week deadline per lesson, but it only starts when I begin the lesson.
No, the deadline really had no bering on motivating me to start. Learning the subject was motivating enough for me. But once I realized I was falling behind, my state of mind changed.