"[T]he biggest market-related risk in target-date funds isn't bonds -- it's stocks. This belief extends to the most conservative target-date funds, where equity allocations typically run between 30% and 50% of the portfolio. And it's especially true today, when we're eight years into an equity bull market and every valuation metric for equities is above historical averages.... It's also a healthy reminder that the types of bonds matter. Shortening the duration of your fixed income exposure and/or overweighting corporate bonds at the expense of U.S. Treasuries may leave your target-date funds underexposed to the very bonds that have delivered the best results in equity bear markets."