As President Barack Obama on Thursday talked up the economic benefits from the wave of home refinancing sweeping the nation, a mortgage broker said he and First Lady Michelle Obama would likely do well to stand pat with the 30-year mortgage they have on their stately mansion in Chicago. *snip* The Obamas, however, do not need to worry about lowering their monthly expenses as much as most Americans, and their Washington housing is free. Back in Chicago, they have a mortgage locked in at 5.625 percent, compared with the current national average of about 4.87 for a standard home loan....