On Saturday I put up the tree and one of my first acts was to put on the lights. I noticed that one of the strings of light had several bulbs out in a row. That is pretty unusual because they are the kind of lights which are supposed to all stay lit if one goes out. I just thought this was a curiosity.
THEN I put my hand up to adjust an ornament and felt another lightbulb which was way hotter than any of the others. I took a good look at it and saw that it was melting its socket!!! Of course I unplugged the entire strand and threw it all away. I had bought them in 1997 and they seemed just fine until this year.
I do think it was oh so lucky I found that faulty bulb out of hundreds. I also recommend that you just go ahead and replace your tree lights at least once every 10 years. Better safe than sorry.