Back-to-back two-term prez are rare

On November 2, G.W. Bush assured himself eight years in office, on the heels of his predecessor's eight-year presidency. How common are back-to-back two-term presidencies? Not very. Besides the present day, it has happened in only two other time periods in American history. Each time, there were in fact three consecutive multi-term presidencies (FDR had 12 years). The first period was 1801-1825; the second was 1933-1961.

Number	Name	From	To	Party	Years
3	Thomas Jefferson	1801	1809	Democratic-Republican	8
4	James Madison	1809	1817	Democratic-Republican	8
5	James Monroe	1817	1825	Democratic-Republican	8
32	Franklin Delano Roosevelt	1933	1945	Democrat	12
33	Harry S. Truman	1945	1953	Democrat	8
34	Dwight David Eisenhower	1953	1961	Republican	8

It would be interesting to figure out what is common between these three time periods in our history. What factors fueled the need for political continuity (or conversely, what kinds of events were brought about by extended political continuity)? War is an obvious one - the war of 1812, WWII, and the current war on terror. There may be more fundamental things going on as well.

UPDATE: Even though Truman served for eight years, he was not elected twice (taking over from FDR in 1945). If we only include re-elected presidents, we're left with the 1801-1825 period. If we include continuity of administration due to death/resignation, we also have:

Lincoln/A.Johnson 1861 1869
U. S. Grant 1869 1877
JFK LBJ 1961 1969
R. Nixon/G. Ford 1969 1977