Living to 100 is becoming more common, presenting new challenges for staying healthy and productive well beyond retirement, according to Michael Clinton, a local author and former Hearst executive, in his new book, "Longevity Nation." Clinton described longevity as "living a longer, healthier life for as long as you possibly can." He explained, "All of life expectancy is growing exponentially. If you go back 100 years, life expectancy was 62. Now it's 80. In Asia, it's approaching 90.