Bill M,
The research on frequency of portfolio rebalancing is mixed but generally favors doing it less frequently (attributed to momentum, costs, and possible tax ramifications) rather than more frequently.
The disadvantage of an all-in-one fund is that you must sell shares of the entire portfolio rather than select a particular asset class to sell. When you have a portfolio of many asset classes you can sell the asset class that has gone up enough to need rebalancing to meet many cash needs and, in a bear market, you can sell the asset classes that have held up best to meet cash needs. Today, for instance, you could sell fixed income asset classes and not disturb equity asset classes if you had a portfolio of distinct asset classes. But it they were all in a mutual fund, you'd be selling across the board.
Scott
