Interconnects Roller Coaster Ride

I purchased a pair of Morrow MA-1 interconnects, burned them in 24/7 for 500 hours. At present, I'm at about 550 hours. Each night I now listened to my system for about three hours. For two straight nights, the sound is gorgeous with the Morrows. Then the third night things sound bad. This pattern has repeated itself twice now. My assumption was that once the interconnects have been fully burned in, they will stabilize and will always sound good. Has anyone experienced this continued roller coster ride in good-to-poor sound from the Morrows?