The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.By Laura L. Carstensen, Professor of Psychology and Director of the Center on Longevity at Stanford University NEW YORK ( TheStreet) -- It seems that national discussions about retirement quickly turn to the long-term viability of Social Security. The problem with focusing too closely on Social Security is that the conversation quickly devolves into one about budgets. The problem with retiring in the early 60s isn't just a problem for Social Security. It's much bigger. We are squandering the opportunity to redesign life. Life expectancy increased by nearly thirty years in the last century and we've tacked them all on at the end. It's not just Social Security that's in trouble. The current model of work and retirement isn't working for most Americans. In the 1930s, it made sense to get an education, work until 65 and retire. But now that people are more commonly living into their 80s, 90s or beyond, that means Americans are routinely spending two and three decades in retirement.