There are a number of sites available to predict longevity based on the variable known to lengthen or shorten one's lifespan. Most ask life-style questions, related to diet, smoker or not, and like this one, alcohol consumption. Questions on the amount and frequency of exercise, the number of relatives expiring due to life shortening diseases are also common. The environment of your residential location is also a consideration -- the air in Iowa is cleaner than in Jakarta, for example. The better calculators express the results as probabilities, in addition to identifying the most likely number of additional years one has to play with. The ones I have looked at place my life expectancy between 85 and 95, with most ending up in the shallow end of the pool.
Why is it important? For one thing, it is good to have some idea how long you are expected to live when deciding when to begin taking one's government mandated retirement benefits, in the USA benefits mandated by the Federal Insurance Contributions Act (FICA) or Social Security. Most people can take the benefit at an age between 62 and 70; the longer you defer, the higher the monthly benefit payments. If you are in ill health or have a long list of unhealthy habits, better to take the benefits early, but if in good health, have a healthy lifestyle and can continue to work or have alternate income sources, waiting until age 70 pays big dividends.
The dividend in wait until 70 comes only if you live beyond the break even point. In my case, the total amount of benefits paid with an age 62 versus an age 70 retirement will be equal at approximately age 78. (66 versus 70 is age 82.) If I was a sickly bastard or had a lifestyle similar to Keith Richards, I would start taking the benefits as early as eligible. But seeing as I am a clean living, wholesome and healthy guy, I am waiting for age 70 as it's more probable than not that I will live beyond age 78 and even beyond age 82, at which point I will probably be money ahead.
More importantly, the benefits that will continue to accrue to my wife, once I hit the silk, will also be greatest if retirement is deferred to age 70. And actuarially, she will likely outlive me by twenty years or more.
