When my mom passed away 10 years ago and I had an estate sale, the first items that sold were her Charlie Brown 1960's artificial Christmas tree, and all the lights, and all the exterior Christmas lights.
We have all our old incandescent Christmas lights boxed up as we bought LEDs years ago to replace them. The wiring is all still safe, and they work fine, if any of the LEDs die putting the old lights back into service would be cheaper than buying new LEDs......even factoring in the higher energy use.