Not only will religion extend your life, it also eases the fear at end of life. A friend of mine is a hospice nurse and a Christian. She once told me that although she is not to discuss religion unless the patient initiates the conversation, the non-religious are much more fearful and agitated during the last days of their lives. Those who were religious were more peaceful and calm during their last moments. A belief of knowing there is something better waiting for them after death combined with the belief they will be reunited with loved ones; was a great comfort in their last moments as well as a comfort to the loved ones surrounding them.
The theory that results from this data is that regular church goers, people who attend church at least once a week, have a better support group of friends and family. Especially when it comes to a crisis in their lives. They make better lifestyle choices such as reduced smoking and little or no alcohol. They are less likely to return to smoking or alcohol as well. Due to these traits the incidence of depression is be lower as is stress. These aspects alone, better lifestyle and lower stress due to better support system are significant factors to a longer life.
Then again, no one can rule out a little help from above to those who are faithful.