Over a five-year period, fewer than half of all U.S. equity funds stick with the same kind and size of stocks, according to Standard & Poor's. That inconsistency can make your portfolio far riskier, or more conservative, than you intended.
"You can't just put your investments in a closet and open it up at age 65 to see how you've done," says David Bergmann, a financial planner in Marina del Rey, Calif.