At the same time, funds that go heavily into bonds in an attempt to shield assets from sudden drops in the later stages of college savings should also be monitored.
Given the expectations for higher interest rates, which could batter bond funds, Fox at Fox College Funding prefers cash when moving money into so-called safer options.
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"When you look at where short-term bond fund yields are, there's not much of a difference between that and cash," Fox said. "I'd rather have the insurance policy of cash."
Further, noted AKF Consulting Group's Feirstein, "a bond fund is not riskless."
In 2008, for example, investors in Oregon's 529 plan were blindsided by severe losses in one of the plan's holdings, the Oppenheimer Core Bond fund, which lost nearly 36 percent that year. The state of Oregon sued the fund company the following year.