STORING THE SAVINGS Wouldn’t taxes eat into the returns from the money you’d save instead of making extra mortgage payments? Not if you place it into an account shielded from taxes. A Roth individual retirement account would fit the bill here, as would a 529 college savings account or health savings account.

Bruce Primeau, whose note to his financial planning clients at Wide Financial Group in Minneapolis on this topic inspired me to re-examine it, adds that this isn’t simply about keeping more assets under his watch so he can earn a better living. “I’m not telling them that the money has to come to me,” he said. “A 401(k) match beats the return on paying a mortgage off automatically. There’s real estate and buying employer stock through a purchase plan at a 15 percent discount and all kinds of things.”

Then you need to preserve those savings. When extra money goes toward a mortgage, it’s hard to get at it when the urge strikes to flee to an Asian beach for a few weeks of playtime. If the money is not locked up in retirement or college savings, however, you may be tempted to spend it.

THE LIQUIDITY PROBLEM Capital-gains taxes might eventually come due with some of these investments, and the rate could well rise above the current 15 percent long-term rate before too long. Still, having some of your savings in a taxable account makes sense for several reasons.

If you hit a stretch of long-term unemployment after having plowed most of your extra cash into paying down your mortgage, your bank probably won’t pat you on the back for being a good saver and give the money back to you. Nor is it likely to let you borrow it through a home equity loan if you have no income with which to repay it.

Elaine Scoggins, who had the mortgage department chief reporting to her at a bank before she became a financial planner, suggests imagining a situation where you need to move quickly but can’t sell your home or extract equity to use as a down payment in your new town. Given that possibility, why create more home equity through extra mortgage payments than you have to?

“The whole housing debacle has reminded us all, including me, that real estate is not liquid,” said Ms. Scoggins, who is the client experience director for Merriman, a planning firm in Seattle. “And it takes cash to support it.”