People might try to enjoy life more while they can. People would think more short-term and less long-term in terms of accomplishing things, having fun, their diets, activities that can affect joints and cartilage, etc. People might get married or into committed relationships sooner. People might have to have kids sooner which would be encouraged out of necessity. Dying early and not living a full life/until old age would have a different meaning. Someone might not care if their risky hobby kills them in their 20s or 30s because they only expected to reach their 40s anyway and not their 70s or beyond.