Life expectancy of a population, in the form of a "death number" can be thrown off by various factors.
In Jesus' time, it was distorted by childhood mortality rates among other circumstances.
In this time and place (circa 1-29AD Roman Empire) what was the common "threshold of old age?" (withstanding cultural discrepancy, perhaps 60-70 in modern day United States & Canada). Life Expectancy does NOT = Threshold of Old Age
Threshold of Old Age = Age number that most people in given culture are considered to be aged, old, and elderly.