This chapter offers a comprehensive account of how person–job misfit develops and unfolds across the working lifespan. Drawing on lifespan developmental, person–environment fit, and conservation of resources theories, the authors conceptualise misfit as the experienced and undesirable misalignment between personal resources, such as needs, motives, and abilities, and what the job offers or demands. They introduce four key dimensions of misfit: excess or deficit of resources, controllability, temporal focus, and duration, and explain how these evolve through career stages and life events. The chapter distinguishes between gradual, accumulation-based misfit and sudden, event-triggered misfit, examining how age-related changes in motivation, ability, and priorities shape both the experience and management of misfit. The authors show that misfit outcomes vary with age, ranging from heightened stress and withdrawal to adaptive behaviours such as job crafting and emotion regulation. They argue that organisations can mitigate the effects of misfit through tailored human resource practices that maintain, develop, or accommodate changing employee needs. By reframing misfit as a dynamic and developmental process rather than a static state, this chapter extends misfit theory to encompass aging, adaptation, and lifelong employability, providing a unifying model of how individuals and organisations co-manage fit over time.