Less than that, probably. You don't really need to be able to do a large number of different things to defend yourself. You need to know the basics of how to escape someone else's grip, how to evade an attack, and be able to put your body weight into a strike, and how to recognize an opportunity to escape. I learned most of that in the first three weeks.
While there are certainly new and valuable things that you learn as you go up in rank, the simple fact that practice makes permanent is half the reason we keep going to class. Your body needs conditioned, and your mind needs conditioned to go full tilt all the time. Half-hearted practice is worse than no practice at all! Self defense is not about having a bunch of techniques. It is about having tools you can rely on without thinking about them, and being ready to apply them when the time comes. Thus, all the training after learning basic techniques. It is about being able to apply them when the time comes.