Oh boy, I've meen waiting a long time for an IMM question... :)
During the early 20's, Vincent became involved with a shipping concern,
the Roosevelt Steamship Company, organized by Kermit Roosevelt with a few
friends. Joined in 1927 by John M. Franklin, son of P.A.S. Franklin (who had
since 1916 been president of IMM), Roosevelt Steamship eventually (1930) staged
a takeover of IMM. Astor (along with John Franklin and Roosevelt) was made a
vice president of IMM as well as being on the board. I don't know exactly how
long he kept the vice-presidential position, but he was involved in the running
of United States Lines (IMM having changed its name in 1943, long after the
word "International" went out of fashion among Americans) until well into the
50's.
-Rachel