Systemic therapy for metastatic melanoma has been revolutionized over the past decade with the development of highly effective immune checkpoint inhibition, specifically anti-Programmed Death 1 receptor (PD-1) therapy. However, even though one-third of patients will have durable response to single-agent or combination therapy, the optimal duration of therapy is unknown. Identifying the optimal duration of therapy is important, as exposure to anti-PD-1 therapy increases the risk of developing immune-mediated toxicities that can have significant morbidity and are, at times, fatal. It has long been understood that patients with complete responses to high-dose interleukin-2 and ipilimumab typically maintain their responses after a brief treatment course; thus, it is important to better understand the data to help understand the optimal management of melanoma patients treated with anti-PD-1 therapy. The clinical data with anti-PD-1-based therapy and published data on the duration of therapy suggest that patients may not require a full 2 years of anti-PD-1 therapy and that the risk of toxicity may be mitigated by further understanding the mechanisms and kinetics of response to therapy. Although novel markers to help guide therapeutic decision making are under investigation, there is an ongoing need to improve our tools to monitor response to therapy and disease activity.