Three-quarters of middle-class adults say they expect to work during retirement, with 25 percent saying they\'ll be punching the clock at 80, a U.S. survey says.Wells Fargo & Co.\'s seventh annual retirement survey, conducted by Harris Interactive in August and September of 1,500 middle-class Americans, indicated 39 percent of all respondents said they will need to work during their retirement years to make ends meet or maintain their lifestyles. Thirty-five percent said they will work because they want to, rather than out of financial need.\"The fact that the vast majority of middle class Americans expect to work well past the traditional retirement age has significant societal and economic implications,\" Joe Ready, director of Wells Fargo Institutional Retirement and Trust, said in a statement.\"Will people be physically and mentally able to work later in life? What will it mean for young people entering the workforce? And, how does our system of retirement savings need to be reformed to help reduce the savings gap?\"Americans have saved, on average, only 7 percent of their desired retirement nest egg -- a median of $25,000 in retirement savings versus a median retirement goal of $350,000, while three in 10 people in their 60s have saved less than $25,000 for retirement, Ready said.Respondents estimated a median of $60,000 in retirement healthcare costs, but a 2010 study from the Center for Retirement Research at Boston College estimated the present value of lifetime uninsured healthcare costs for a typical married couple age 65 will be $197,000.