I agree that there are pros and cons to different ages to start training but I disagree with what you said about being older and material "sinking in easier". I disagree because I think young men and women who come straight from school/college/university are used to full time studying and are more capable of learning and grasping new things, courtesy of their age. If an older person who has maybe been sitting in an office job for say 5 years were to start flight training I think it would feel a lot more intense than someone coming from that studying environment and mentality.