Just some notes for the conversation:
Using modern times (1952 to 2016) as the base reference, the average number of years in office for American Presidents: 5.82
Excluding the Kennedy-Johnson anomaly (death in office) and the average is 6.22
Of the eight modern President's who ran for re-election, only two were defeated.
It's widely accepted by political historians that the general tempo of Presidencies is along the lines of:
Productive, often definitive, first two years until mid-term elections which typically result in significant congressional losses.
A retrenching third year leading to focusing on reelection in the 4th year.
If successful in being reelected, moderately productive 1st year, the last 3 tend to be oriented towards foreign affairs (with mixed results), since domestic agendas are either passed, or DOA.
By the way, even including the entire 20th century, early deaths et al, the long FDR period, doesn't changes the averages.