Light 'em up

Why, can anyone explain, do the tree lights work when I put them away, and when I pull them out, nothing? This year more than half of my tree lights are dead. My tree looks pathetic with lights on only the lower half. I have to buy new lights every year! That is not very green, not to mention a giant pain in my backside. 

Another light related issue, I just asked a child why it was so dark at only 3:30, and the smart response, because the lights are not on. Ah, yes, and water is wet, thanks kiddo for letting mom rant.