Somewhere between 17 and 25, they do indeed become human again - depends on gender, attitude, personality...just hang in there! My #4 is about to turn 20... only 3 more to go!! I always pound it into their heads - gently - that yeah, they are "adult", but they are also legally responsible for what they do. And none so far had done anything too bad - maybe life changing, but not arrestable! And if they are still living in my house? My house, my rules! "Deal with it"!
One of the best moments - when the most rebellious, a girl, called and asked ME advice on mothering!!