Perhaps I'm just paying greater attention to the topic of late, but it seems like a fair number of large statistical studies that correlate exercise with increased life expectancy have shown up in the past couple of years - more than I recall prior to that. A few examples from the archives:

• Exercise, Longevity, and Long Term Medical Costs
• The Power of Moderate Exercise
• Another Study Suggests that Sedentary Behavior Adds Up

Here is a newly published study on this topic that pulls from a data set of around 95,000 people. It is presently open access, which is not usually the case for the journal in question, so take advantage of it while it lasts:

Years of Life Gained Due to Leisure-Time Physical Activity in the U.S.

Data from the National Health and Nutrition Examination Survey (2007-2010); National Health Interview Study mortality linkage (1990-2006); and U.S. Life Tables (2006) were used to estimate and compare life expectancy at each age of adult life for inactive (no moderate to vigorous physical activity); somewhat-active (some moderate to vigorous activity); and active ([more] moderate to vigorous activity) adults. Analyses were conducted in 2012.

Somewhat-active and active non-Hispanic white men had a life expectancy at age 20 years that was ?2.4 years longer than that for the inactive men; this life expectancy advantage was 1.2 years at age 80 years. Similar observations were made in non-Hispanic white women, with a higher life expectancy within the active category of 3.0 years at age 20 years and 1.6 years at age 80 years. In non-Hispanic black women, as many as 5.5 potential years of life were gained due to physical activity. Significant increases in longevity were also observed within somewhat-active and active non-Hispanic black men; however, among Hispanics the years-of-life-gained estimates were not significantly different from 0 years gained.

The estimates in the present study for non-Hispanic white men aged 20 years [suggest] that 2.6 hours [of overall life expectancy] are gained per hour of moderate activity and 5.2 hours were gained per hour of vigorous activity accrued in adulthood.

The effects of exercise on general health over the long term are possibly more striking. You can't exercise your way out of aging, but you can laze your way into a much more unpleasant and expensive later life. Exercise, calorie restriction, and the like are small stopgap measures, the poor and miserable best we can do right now in order to gain a better chance of being alive and in good health to great the arrival of rejuvenation biotechnologies - therapies that will repair and reverse the cellular and molecular damage that drives aging.

We need those biotechnologies to get out of this hole alive. They are the most important goal - don't lose sight of that behind the constant deluge of data on health, life expectancy, and how we can presently modestly adjust the pace at which we're aging to death.

Source:
http://www.fightaging.org/archives/2012/12/years-of-life-gained-due-to-leisure-time-physical-activity.php