Baby boomers started turning 65 in 2011, marking the unofficial beginning of their retirement years. The timing could not have been better for older boomers, who are already part of the wealthiest generation in U.S. history. Since then, the broad S&P 500-stock index is up 91 percent, including dividends. U.S. stocks hit a record high yesterday.

Market performance in the early years of retirement is a crucial worry for anyone living off a nest egg. In the worst-case scenario, stocks crash just as retirees start spending their savings, leaving them in a hole they can no longer earn their way out of.

Older boomers have experienced what is arguably the best-case scenario: The S&P 500 has returned 269 percent since its March 2009 low. As a recent study in the Journal of Financial Planning shows, wealthy retirees can be very cautious about spending down their savings. This instinct, along with the stock market’s new record, suggests that many boomers are likely to end up with far more money than they know what to do with.