Danish fencer Ivan Osiier made his Olympic debut in the 1908 Games in London (#1) at the age of 19. He did not medal there, but returned four years later in Stockholm (#2) and won a silver, tasting early success.
But Osiier didn't stop there. World War I canceled the 1916 Olympics, but he returned in 1920 in Antwerpen (#3), where he did not medal. He didn't either four years later in Paris (#4).
No medals in 1928 in Amsterdam (#5). None in 1932 in Los Angeles (#6). Being Jewish, Osiier boycotted the Berlin Games in 1936. His next appearance didn't come until after World War II, when he returned to London (#7) in 1948, when he was 59. He didn't medal.
So, seven Olympics in a 40-year span. Not too shabby, even if all Osiier had to show for it was one silver medal... which didn't make him the greatest Olympic champion in his family. His wife, fellow fencer Ellen, won gold at her only appearance in 1924.
Maybe that's why he kept trying...