According to actuarial tables maintained by the Social Security Administration, the life expectancy of a 70 year-old man is 14.30 years -- enough time to serve two terms and move on to physical decline. The life expectancy of a 78 year-old man is 9.33 years -- enough to last two terms and not a lot more. The life expectancy of a 79 year-old man is 8.77 years -- barely enough to make it out of the White House. Of course, each man might live to 100. None of us knows. But given their age, the issue is more than just...