Teaching during the course of your Ph.D. is not a mandatory requirement of the course at most of the places. It is a decision which is subjective to the researcher as well as the supervisor. Depending upon the environment you belong to, your teaching options may vary. Some of the departments offer the choice of doing seminars, while others give term long or even yearlong teaching assignments. Quite many research scholars take up teaching jobs during Ph.D. for monetary as well as experience related benefits. A lot of guides encourage their scholars to take up teaching assignments in the final year of their Ph.D. By the last year of their course, they are largely free from the task of research, and thesis writing. It is always advisable to go by the advice of your supervisor, primarily.
As a research scholar, for the future, if you are sure that academia is your calling then getting some teaching experience is surely the way it should go. However, even if you are looking for a career in the corporate, teaching exposure would help you to build up your communication skills, time managing skills, and at the same time train you to be imaginative and flexible at the same time. An effective and focused teacher at the university level is always on a mission. Though he knows his focused goals of teaching, there is always scope for the unexpected to creep up and that surely is a learning experience for all.
You may feel that time is an issue for researchers as they are anyways fighting against time to complete their research on time. But you can handle it by doing some strategic planning. With some consistent effort on a daily basis in planning and preparation, surely teaching assignments can be accommodated easily in the schedule of a scholar.
Not everyone is made of the mettle to teach so you must ponder over the idea before you jump into teaching as a profession. If you feel that teaching isn’t your forte, you can also explore the option of becoming a mentor for the students. It is also a fulfilling and learning experience, and also a great help to distressed students or students in need of guidance and support. By and large, taking up some teaching jobs during the doctoral tenure wouldn’t make you lose anything, and surely make you have an insight into the profession. Just ensure to follow your guide’s opinion.