Just a little historical note:
Last World War I vet in United States was Frank Buckles, who died on 27 February 2011 at 110 years old.
http://www.cnn.com/2011/US/02/27/wwi.veteran.death/
I met a Spanish-American war bet in the 1964 when he was in his 80s. It was interesting to meet a living relic of another time.