From 2012-2015, Advanced Placement (AP) science courses underwent a large-scale curricular reform to include more scientific inquiry and reasoning, reduce emphasis on broad content coverage, and focus on depth of understanding, with corresponding changes in high-stakes AP examinations. In this study, we explored how teachers prepared for and adapted to this reform over a three-year period. Data included four waves of individual interviews with 22 AP Biology and Chemistry teachers across the United States. Data were qualitatively analyzed using emic and etic coding. Four themes were developed from these data: (1) initial perceptions about the reform including uncertainty, anxiety, and excitement, (2) preparation for reform, (3) impact of time, and (4) intersection of affinity toward the reform with time and uncertainty. Although teachers faced a variety of implementation challenges, these did not always influence their professional development (PD) choices. Rather, choices were more often driven by the price and proximity of those activities, resulting in a jumbled mélange rather than a coherent, extended series of learning experiences. Despite a variety of attitudes, beliefs and instructional skills, teacher beliefs about the purpose and value of the reform--over and above their learning experiences--influenced the time needed to transition and to become comfortable with the redesigned course. This study has implications for how teachers may respond to large-scale, top-down, curriculum reforms (e.g., NGSS, Common Core) and how education leaders, policy makers, and PD providers might support teachers in their efforts to adapt efficiently and effectively.