While doing a bit of research on a political attack email circulated over the weekend I came across this fact. In 1994 Congress changed the law so a US President first elected after 1997 will receive up to 10 years of Secret Service protection after they leave office. Before the change presidents since 1965 had been entitled to lifetime protection.
There is an interesting related paradox. In the late 18th century, when the United States Constitution was written, the average life expectancy of a newborn baby was 35 years. Now 200 years later the life expectancy of a newborn is more than 80 years. (This simplistic observation does not adequately take into account age-adjusted life expectancy of a person surviving childhood diseases that are much less of an impact on today's statistics than they were two centuries ago.) The point being the founders of the country envisioned the president as not only a mature person but possibly an elder statesman. In this context it is interesting that in more recent times as newborn life expectancies have grown longer we've had some of the youngest presidents yet to serve. Although the late 20th century also brought the oldest American President ever elected so all this could mean very little.