The fastest successful mission I've ever seen ended in about 12 minutes. I've also seen them go for hours. "Party Crashers" usually takes a little less than 30 minutes; "Havoc in the Hamak Sector" usually takes about 45 minutes.
Of course an unsuccessful mission can end in less than a minute . . . if your helmsman runs over a mine.
"Damn the torpedoes! Four bells, Captain Drayton!"
(Likely actual words of Admiral David Farragut, USN, at the battle of Mobile Bay. Four bells was the signal for the engine room to make full steam ahead).