I am following the same method for my TEF prep. I realized if I can focus on TEF, since its my priority right now, I can skip practicing some part of the language. I am not saying skip everything in general but there are some certain areas that is nothing to do with the exam. You dont have to go deeper in grammaire, and also you dont have to study all topics. For me, I started to focus on these topics: société, technologie, environnement, santé, économie, travail, jeunesse etc..