Just wanted to add one more thing - my parents had kids in two "groups" kind of, the first 6 of us from when they were 22 - 32ish, and then 2 more around 40, and they often comment on the difference in energy level from when we were little, to how they feel now with my littlest brother and sister. I can remember going skating and sledding with my parents and it was great! We went camping more, and played "tackle Dad" and they just can't do that any more! Also, we older ones notice that they don't seem to have the energy to discipline the way they used to!