This paper is based on a study conducted ten years ago at one university in Japan aiming at collaborative development through reflection among a teacher educator, two in-service teachers, and four pre-service graduate students. Collaborative reflection involved methods, such as the graduate students' observation of the in-service teachers' English language lessons and the joint journal entries among the three parties. Though the teacher educator and in-service teachers had attempted to facilitate the graduate students' engagement in reflection, the research seemed to have finished with a sense of incompleteness. The present study, through taking the autoethnographic and duoethnographic approaches between an in-service teacher and the teacher educator from the past study, reexamined the past data for continuing professional development. The research question posed is how we develop as teachers/researchers through dialogues with the past self and the past research partners (graduate students and the other in-service teacher), and collaborative dialogues with the current co-researcher. The intricate interplays of the self, the co-researcher, and the past students across time brought forth multidimensional arenas for reflection. The study suggests the benefits of reflection on previous data for continuing professional development as reflective practice is a collaborative and iterative learning endeavor.