Normal and abnormal differences in sustained visual attention have long been of interest to scientists, educators, and clinicians. Still lacking, however, is a clear understanding of how sustained visual attention varies across the broad sweep of the human lifespan. Here, we fill this gap in two ways. First, powered by an unprecedentedly large, 10,430-person sample, we model age-related differences with substantially greater precision than prior efforts. Second, using the recently developed gradual-onset continuous performance test (gradCPT), we parse sustained attention performance over the lifespan into its ability and strategy components. We find that after age 15, the strategy and ability trajectories saliently diverge. Strategy becomes monotonically more conservative with age, whereas ability peaks in the early forties and is followed by a gradual decline in older adults. These observed lifespan trajectories for sustained attention are distinct from results of other lifespan studies focusing on fluid and crystallized intelligence.