Multiple facets of well-being are known to show steep end-of-life deteriorations. However, the underlying mechanisms and pathways are vague. Capitalizing on an earlier review of the existing empirical literature on terminal decline, we present a conceptual/methodological framework that can be used as a tool to structure future inquiry aimed at refining the precision and specificity of the terminal decline concept. Specifically, we propose a model of terminal decline in well-being in which within-person mean levels of, inconsistencies in, or couplings among multiple domains of functioning serve as indicators or sources of well-being. The model, based on time-varying dynamic factor analysis of intensive longitudinal data, provides for concise articulation and testing of central tenets of theories of successful aging, including hypotheses regarding shifts in goals away from some domains and towards others (e.g. secondary control). We conclude by suggesting routes for empirical research.