In this commentary, the common themes from the interesting articles in this special section of Developmental Psychology are considered as they illuminate the potential ontogenetic sources of the conscientiousness-well-being-longevity interconnections that have emerged in recent research. In particular, consideration is given to the changing nature of the expression of conscientiousness over the life course and the importance of the causally linked chain of developmental events associated with the sustenance of this trait from early childhood to later life. Methodological as well as conceptual issues are part of the common thematic analysis provided. In addition, several more or less neglected issues are addressed in the commentary. These include an examination of the potential roles of self-presentation social context and social aggregation in the developmentally emergent conscientiousness-well-being relationship. Further, the potential downside of the moral tinge of the conscientiousness construct is considered, as is the cultural variation in the benefits of conscientiousness to well-being. Finally, the applied significance of research on the conscientiousness-well-being link to health promotion over the life course is addressed. The commentary concludes with reflections on the transformation of 1970s trait-like conceptions as unbending tautological predictors of behavior into the situationally and developmentally nuanced conceptions of conscientiousness provided in these collected articles.