As people are living longer, the approach to target retirement funds is shifting away from safe and conservative toward more risky investment, MarketWatch reports. Traditionally, target retirement funds grow more cautious as the investor nears retirement age. For a retiree, your risk is longevity risk having your assets exhaust themselves while you still need income, Jonathan Shelon of Fidelity Investments told MarketWatch. These days retirement can last four decades or longer, and the need for money will grow with their old age. As a result, the investment mix is now more likely to contain a larger percentage of stocks than it used to, rising from a 50% allocation to stocks to a moderately aggressive 80%. The Vanguard Group, says MarketWatch, has ratcheted up its stock allocations after a shareholder survey indicated that respondents were comfortable with increased risk.