There are many things said to affect length of life. Some studies that have come out recently show that restricting caloric intake can lengthen life: low calorie diet Also, Seventh-day Adventists were featured in a comprehensive study recently, showing the vegetarians tend to live longer, and the more vegetarian you are, the longer you tend to live: Adventist Health Studies Fast walkers tend to live longer too: walking speed effects Living in a “rich” country tends to help, and having faith has been shown to statistically increase longevity: faith matters in longevity.
However, there are some factors tending against me: Marrieds tend to live longer, people with pets tend to have longer lives, and people who have agricultural pursuits usually live longer.
But the secret to really long life is given clearly by Jesus in John 17:3 “And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.”