After spending over $800 million dollars to build them and get them there for a nominal 90 day mission, and having survived a first six month extension beyond that, NASA has come up with another $2.8 million to extend the missions another 6 months. The craft are still in good working order. Opportunity will take the chance and make a 3 mile trek over to a large crater, Victoria crater, with a stop at its heat shield along the way.
http://www.space.com/missionlaunches/rover_extension_040921.html
http://www.space.com/missionlaunches/rover_extension_040921.html