According to my superficial internet 'research', the oldest living examples of the crepe myrtle are in Italy and are about 130 years old. So our examples, which are well over 50 years old by my estimation, are middle aged but still very much in the prime of life. They will probably outlast my wife and me, which is not something I want to contemplate for too long. At the moment, though, I'm more concerned with whether they will survive the current drought/deluge pattern of precipitation in the Southeast that is stressing so many trees. But for as long as they are around, they will remain excellent subjects for photography.
