Before I strung those blue lites up again this year, I plugged them in to check them. There was only one segment in the first strand that was lit - all but one of the segments were dark. And there were dark segments in the second and third strands as well. So I painstakingly went thru, LED by LED, to look for problems. What I found was discouraging.
It seems that these particular LEDs have leads made of iron. I am not familiar with the manufacturing process for LEDs, but one would suspect that those intended for use in an outdoor environment would not use tiny, fine, iron wires. Nevertheless, these did. That pile of bulbs represents hours of fingernail-tearing work in the cold, pulling hundreds of bulbs. The failures all had leads which had disintegrated into rust powder. And perhaps not surprisingly, the fixtures themselves are only vaguely waterproof. I suppose I am getting my just deserts for buying the cheapest lite strands I could find.
So, after I finally had all the segments glowing once more, I strung them up.
One segment went out (it's near the mizzen mast).