A Final Lesson of Home presents a conceptual framework for rethinking cultural memory preservation through the household as its smallest institutional unit. While existing heritage systems primarily document exceptional individuals, collective traditions, or historically significant events, the everyday lived experiences of ordinary families remain largely unrecognized and structurally unpreserved. This work proposes a household-based cultural memory system designed to address this omission. The framework introduces a voluntary, low-threshold approach that allows families to preserve fragments of lived experience—such as short narratives, images, or reflections—without requirements for completeness, historical significance, or continuous participation. Incompleteness and interruption are treated as inherent conditions of everyday life rather than failures of documentation. A central contribution of this framework lies in redefining the institutional role in cultural preservation. Instead of curating or evaluating content, institutions function solely as providers of long-term infrastructural stability, ensuring continuity across generations while remaining non-interventionist with respect to meaning and representation. Published as an independent conceptual framework, this work is intended to serve as a reference text for researchers, designers, cultural practitioners, and policymakers exploring new models of heritage preservation, family-based memory systems, and long-term cultural continuity. It may be cited, adapted, or extended in academic, cultural, or institutional contexts.