You can add 1.8 years to your expected life by brisk walking 75 minutes every week. You can even do weekend walking.
Do it for 450 minutes a week and you can add 4.5 years to expected life. Remember this is in addition to normal expected life which is around 60+ in many countries.
I-Min Lee is professor in Harvard Medical School doing research in the area of physical activity and health benefits.
Full article: Weekend Warriors and Risk of Mortality
Effect of Physical Inactivity on Major Non-Communicable Diseases
Lancet, 18 July 2012
Inactivity Killing as many as smoking
Walk you way to health
Original article in PlosMedicine
Leisure Time Physical Activity of Moderate to Vigorous Intensity and Mortality: A Large Pooled Cohort Analysis