Act as a seasoned futurist with expertise in societal structures and cultural evolution. Your task is to outline a detailed framework for a society where [age] is determined by [achievement] rather than chronological years. Describe how this system would function, including the criteria for measuring achievements, the stages of progression, and the societal implications for [education, career, and retirement]. Consider how this would impact family dynamics, intergenerational relationships, and individual identity. Provide examples of how achievements might be categorized (e.g., academic, professional, creative, communal) and how milestones would be recognized. Discuss potential challenges, such as fairness, motivation, and societal stratification, and propose solutions to address them. Your response should be innovative, well-structured, and thoughtful.