I love that we are even having this conversation. When I started this game I remember wondering how anyone survives a week, let alone long enough to get bored and now I routinely "retire" characters because I feel like they are stable enough to say that whatever got them was not worth playing through until. Some amazing suggestions have already been made but I think it stands to reason that after a certain point the main threats are not really the zombies. The first wave kills people because most people don't respond to emergency situations by smashing the brain of a crazy person. One the only people left are those that are brain bashers the threat comes from things like those suggested above. Storms, raiders, disease, and so on. Keep up the great work folks.