Wonder if they have a giant bird feeder as well?
Wind chimes are at their worst when they're neglected, the clapper lists at an angle and only strikes the same couple of notes each time.
Some of our neighbours here have bamboo ones which aren't quite as bad and luckily can't be heard from the house.
Why not pop round to your neighbours and tell them that your sleep is being disturbed - they will probably go out of their way to recommend herbal teas and essential oils that will help you sleep through the noise