Interesting! The part about solenoid current causing heat and thus reducing the life of the solenoid is the bit I'm potentially concerned about. I don't think the little relay box that came with my HIDs (and which I'm not using) has a circuit to reduce solenoid current. Perhaps I'll cut it open to see.
The particular controllers in that eBay auction are for Bosch Bixenon HIDs which have two solenoids - a high-power one to move the shield and a low-power one to hold it in place.