How has your experiences with the passage of time changed as you aged? I see the phenomenon as a function of information gain. Every new day for a child is filled with the unknown that must be assimilated rather than reduced to similar experiences/concepts. This so called "spark of life" or authenticity to experience is what slows down the passage to time; conversely, routine accelerates this pace as little information is gained (e.g. dreams aside, losing and regaining consciousness during sleep is a massive acceleration in time).
So the second question is, how does one keep life afresh as one ages? Jung speaks of individuation through the inferior function which is consistent with the idea that it forms a new basis of information that the ego has rejected upto this point. So, penny for your thoughts?