My wife says the Corvette is still THE mid-life crisis car. Since Corvettes, Porsches, etc.. are not really muscle cars like a Shelby Mustang I think the 40-something Shelby owners are just the generation that always wanted a Shelby Mustang and not seeking something to satisfy their mid-life crisis. But I might be full of crap. I did order a Mustang from the factory when I was 21 years old. That wasn't a mid-life crisis. It was a crisis to gain a little speed and performance from Ford without paying the high cost of some foreign car.
Oh, it's a mid-life crisis for me!