Many researches on interaction design that supports users behavior change in everyday life are studied recently especially in the domain of pervasive technology. However, not much attention has been paid to long-term effects on users in such cases. This paper presents our initial work of a long-term (8 month) study of users self-report of experiences with an ambient dashboard feedback system in an automobile called Eco-driving system. It was notable that user satisfaction changed positively following active self-efforts made by users to understand the system after the negative shift due to initial disappointment. This work will be a first step to build a framework of how users accept systems designed to persuade them to change behavior over time.