Different people have different lifestyles. But it appears that it matters most where in the world (rather than how) you live. Health care and hygiene seem to influence life expectancy more than any other factor (from the CIA World Fact Book):
Even habits such as smoking do not seem to have a major influence: Japan, a country with lots of tobacco consumption, has the highest life expectancy in the world (80.91 years, CIA Fact Book 2002). Hong Kong, a dense 7 million people city with constant stress, follows Japan closely (79.8 years, CIA Fact Book 2002).
Food and lifestyle make rather a small difference (all from CIA World Fact Book 2002):
Scientists are working to extend our life, mainly with these ideas:
It is believed that life expectancy in First World countries will have risen to 100 years by 2030, and to 120 years by 2060.
(Please add to this list.)