Sometimes I play a shorter version of this in which 2 sim days = 1 year and the lifespan is 150+ sim days. When playing TS3, I prefer a 300+ sim day lifespan in which 4 sim days = 1 year.
To me these numbers do not make any sense.
As I have read on a number of forums, many players do not like these lifespan settings and because of that will either play with aging off or they will manually age-up all the Sims.