Under Pressure

An interesting article and 2 years worth of sacks should provide a large enough sample size for the statistics to be fairly accurate.

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The median sack time has hovered between 2.7 and 2.8 seconds throughout the two years of the tracking.

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While it has not been possible to log each and every pass attempt around the league, over the past offseason it was possible to log the time of pass for all of Steelers pass attempts in 2010. Since Roethlisberger is considered to be prime example of a quarterback who creates big plays by holding the ball and escaping sacks, his statistics are useful.
What was found was that in Roethlisberger’s case, his sack percentage (the percentage of pass plays that results in sacks) goes up significantly the longer he holds the ball. Roethlisberger’s sack percentage doubled when he held the ball for longer than three seconds -- seven percent for passes of 2.1 to 3.0 seconds, 14 percent for passes that took between 3.1 and 4.0 seconds. Interestingly, his quarterback rating, yards per attempt and first down percentage all dipped when he held the ball for more than three seconds, so it’s difficult to say that holding the ball longer really pays off for Roethlisberger.
On the other end of the spectrum, when the Colts lost Peyton Manning to a neck injury, they not only lost one of the best quarterbacks in the league, but they also lost a quarterback who could make their offensive line's potential weaknesses seem to disappear. Over the past two years, Manning has been sacked only 26 times. When you look at sacks that are created by a quarterback holding the ball too long, however, Manning is even more exceptional. No other quarterback can top Manning’s four sacks of three-plus seconds in 1,250 pass attempts (0.32 percent of attempts).

http://footballoutsiders.com/under-pressure/2011/under-pressure