Good information, so essentially the Gulf War never ended, and war powers have been active since 1990.

> Mexican Border Period (May 9, 1916 – April 5, 1917 for Veterans who served in Mexico, on its borders, or adjacent waters)

> World War I (April 6, 1917 – November 11, 1918)

> World War II (December 7, 1941 – December 31, 1946)

> Korean conflict (June 27, 1950 – January 31, 1955)

> Vietnam era (February 28, 1961 – May 7, 1975 for Veterans who served in the Republic of Vietnam during that period; otherwise August 5, 1964 – May 7, 1975)

> Gulf War (August 2, 1990 – through a future date to be set by law or Presidential Proclamation)

That makes the Gulf War the longest war combined with the terror wars from the article (2001-present). We are only 15 years into this century and already have seen as much war as last century which included the world wars. I guess perpetual war has already started.

So the durations increased monotonically, except for WWII as kind-of-surprisingly defined to last through 1946 making it edge out Korea. I didn't expect such a simple pattern.