Tanis - this is exactly why DH has 2 valid US passports, given to him by the state department. The second passport is only valid for 2 years.
VictoriaS - he has two passports b/c he travels A LOT. For example, he will be traveling in Kazakhstan on one passport. While at the same time his other passport is being sent off to an embassy for a visa to Uzbekistan. He'll come back to the UK for a day or two, trade out his passport for the one with the Uzbek visa, fly to Uzbekistan while the other passport is then sent off to some other country for another visa. So when he's traveling on the one without the UK visa it's a pain.