Gamified Authentic Mobile Enquiry in Society (GAMES) is a GPS-supported mobile application for gamifying social enquiry learning in outdoor environments. Teachers are always the "educational innovation gatekeepers" in schools. This paper reports on a 3-year study in which the Stages of Concern model was employed as a quantitative diagnostic instrument to continuously understand and address the emerging concerns of 91 social humanities teachers (from 91 high schools in Hong Kong) about adopting GAMES in their teaching practice. With adequate interventions for addressing the participants' ongoing needs, their peak categorical concern shifted initially from "Management" (in Year 1) to "Consequence" (in Year 2), and finally to "Refocusing" (in Year 3). The results reveal that the participants largely intended to go on harnessing GAMES to facilitate outdoor social enquiry learning in their schools. This work provides the field with profound strategic insights into sustaining technological innovations in schooling from the perspective of teachers--an important stakeholder of education.