We've talked in previous classes about the dangers of becoming a collector of investments. Not only is it more difficult to keep tabs on a large number of investments, but oftentimes "collectors" make investments for the wrong reasons and lose sight of their goals.
So are investors with multiple portfolios prone to become collectors? Not necessarily. True, investors with multiple portfolios may have more investments than investors with one portfolio. But if their goals are the driving forces behind their portfolios, multi-portfolio investors will not become collectors, no matter how many investments they actually own.
Further, multi-portfolio investors don't have to own dozens of investments across a variety of portfolios. They can choose a handful of securities that they like and understand and use these securities in their retirement, college-saving, and other portfolios.
For example, you may like TIAA-CREF Growth & Income (TIGRX) for exposure to U.S. large companies, Harbor International (HAINX) for foreign stocks, and Vanguard Total Bond Market (VBMFX) for bonds. You could plausibly use only these funds in all of your portfolios (if they're available in your retirement plan, that is). You'd simply adjust your weighting in each depending on your time horizon.
In fact, depending on how many investment goals you have, you could have more portfolios than you have investments. That's fine. It all depends on your goals.