Just for a bit of perspective, this mission began on June 10th 2003 with the launch of the Spirit, touching down on January 3rd 2004. I'm not sure, but I believe the rovers planned tour of duty was 90 sols. I just confirmed it. As of May 2007, Spirit surpassed 1200 sols, more than 13 times the anticipated length of service.
Since 2004, both rovers have sent a steady stream of scientific data about the surface of Mars. I love reading about them, and I can't believe I've missed this much over the past few months.