Tad and his wife are about to send their last child out of the home and off to college. what stage of the family life cycle will tad and his wife enter when they are the only ones living at home?

It’s called empty nester

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle