Size alone has limited predictive power for lifespan. Consider the example of the naked mole-rat (30-35g, 31 yr) vs Norwegian rat (450g, 3 yr). Naked mole-rats dwell in environments shielded from predation, whereas no R. norvegicus in the wild could possibly hope to avoid attrition for 10 years, even if its ageing process allowed 20 years of healthspan, let alone 30.