Thanks to medical gains, a 65-year-old man has a 60% chance of living to age 80 and a 40% chance of reaching 85. For women, the odds are 71% and 53%, respectively. All of this has made the 85-and-over age bracket the fastest-growing segment of the population. In an era of low interest rates, volatile financial markets, and rising costs for health and long-term care, finding money to cover those years isn't always easy.