It sounds as if stretching and proper exercises help to encourage and set up one's posture.
Should not one consciously adjust one's posture when they find themselves getting tired and slipping into a slump or poor posture? This seems to help me.
While we are on this... what about matresses, chairs, and special pillows? I have heard that these things can make quite a difference.
Also, what about sleeping positions? I heard that stomach sleeping, for example, is bad for certain back and hip ailments.