Do You Play Through Each Life Stage or Age Up Whenever?

I used to age up whenever, until we got Infants. I have found (or made a correlation, at least) between allowing the newborn to age up naturally that the Infant seems better equipped to learn the steps they must take. Also, with the added days to Toddler, Child and Teens, it already seems as if the time flies by so fast. (And I play on Long, too.)