re: #4 silverdolphin

I think that the stresses of running the Executive Branch prematurely ages most people. Prime ministers can last longer but not by much. While Thatcher lasted almost 13 years, the average is about 5 years, the maximum length of one Parliament.

Trump is an exception because he really never did any stressful work.

Except for his last couple months in office when he was working overtime to overthrow our government.