"The spacecraft for asteroid sample return mission, MUSES-C, scheduled for launch in May 2003, will have an ISAS-developed microwave ion engine onboard for interplanetary navigation. The prototype model of this engine has achieved 18000 hours of autonomous endurance running. The ion engine that started the endurance test on March 30, 2000 to verify its performance for the mission requirement of 18000 hours has continued autonomous running over approx. 2 and a half years. It successfully achieved the original goal of 18000 hours at 2:00AM on October 25, 2002, and still keeps running at present. The engine used for the endurance test is a prototype model of MUSES-C and has been produced in complete accordance with the design, material and manufacturing of the flight model."

Full article and picture of running engine here.

Now that's *testing* a system!
SteveS