I believe that commitment is an important aspect of distance education. Despite the perceived difficulty associated with studying a subject through distance education, the experience of each student will be different. In addition to commitment, factors that can contribute to a positive learning experience through distance education include perseverance, determination and diligence in your studies.
From your post, it is evident that you have an interest in pursuing History subjects (including History Extension), meaning that, in this case, the personal interest aspect of subject selection is satisfied. Similarly, given your interest in historiography and the fact that you are currently taking Ancient History and Modern History, there appears to be some strong relevance between your subjects and future studies. Based on this, taking History Extension is likely to increase that relevance, which is always a good thing.
The only remaining concern is performance. Here, you should ask yourself a few questions, such as:
- Do you strongly believe that your passion for history will be sufficient in enabling you to manage an increased workload and ensure favourable performance across your subjects?
- Have you considered your current performance, especially in Ancient History and Modern History, and the effect that taking History Extension may present upon those?
Of course, if History Extension through distance education ends up not working as intended (for example, you find the workload to be unmanageable, or you find it difficult to stay up-to-date with the content), dropping it remains an option, allowing you to shift your focus towards your other subjects.
I hope this helps!