As repetition of activities can establish habits and exploration of new ones can provide a healthy variety, we investigate how a recommender system for physical activities can optimally balance these two approaches. We conducted an eight-week user study with 62 physically inactive participants who receive personalized repetition and exploration recommendations in a random order. We distinguish between location, workout, and general activities, and collect participants' subjective perceptions. Our findings indicate that participants initially preferred exploring general activities, but rated repeating recommendations higher after two weeks. By exploring the optimal transition point from exploration to repetition in personalized recommendations, this study contributes to designing more effective recommender systems for health improvement and healthy habit formation.