Cozies give you a little more latitude to have the body show up later. I always think it's more interesting to see the amateur sleuth interact with the soon to be dearly departed before they actually depart. Delaying the murder gives you an opportunity to plant potential clues regarding motive and potentially show why the sleuth would choose to investigate that particular murderer. Cozies are as much about the relationships between the characters as they are about the murders.