Oscar Trivia, Weekly: Double Oscar winners... How long does it take?

For today's utterly random weekly Oscar trivia, how about two-time acting winners? For the purposes of this list we're ignoring the rare third wins (that list only includes six people: Streep, Hepburn, Nicholson, Bergman, Brennan, and Day-Lewis) and focusing on the gaps between the first and second Oscar wins. What is most common for the double-dippers?
Marlon Brando's two wins...
ALL THE DOUBLE-WINNERS
+ GAPS BETWEEN OSCAR WINS
FROM LONGEST TO SHORTEST
01
Helen Hayes (38 years: The Sin of Madelon Claudet to Airport)
02
Katharine Hepburn (34 years: Morning Glory to Guess Who's Coming to Dinner)
03
Frances McDormand (21 years: Fargo to Three Billboards)...