Recent research investigating the course of affective development across the adult life span has incorporated both cross-sectional and longitudinal data in analyses to understand the aging-affect relationship. Most of these studies, however, have not provided an empirical test to determine whether the cross-sectional and longitudinal data can be combined to infer developmental processes. Utilizing an age heterogeneous sample followed over a 10-year span (N = 1,019, Mage = 54.14 ± 13.06), the present study used an accelerated longitudinal design to investigate whether cross-sectional age differences could be found in longitudinal aging trajectories of positive affect (PA), negative affect (NA), and their confluence (i.e., affect optimization, the experience of PA relative to NA). Additionally, age-related differences in poignancy, co-occurrences of PA and NA, were examined. Absence of cross-sectional age-differences in the estimated longitudinal aging trajectories of PA and affect optimization suggested that a developmental process could be inferred; whereas, the longitudinal aging trajectories for NA showed cross-sectional age differences. PA and affect optimization showed a cubic relationship with age; NA showed decreases across adulthood; and poignancy showed age-related increases across adulthood. Self-rated health was investigated as a covariate in all models. Though somewhat more nuanced, the estimated trajectories for PA, NA, affect optimization, and poignancy provided support for theories of affective aging. The implications of these findings, directions for future research, and issues surrounding using cross-sectional data to infer developmental change are discussed.