Always,always look to the native people of a given area and what they used before the 'advantages' of refined flour, fortified and presliced bread, 40 hour + work weeks and Government housing projects. Homeless people often create ingenious solutions with the 'junk' we threw away along with them. Anything over 72 hours IS longterm survival. It's a given that creating a secure living area greatly increases a person's survival odds and mental well being. I'll crawl into my sleeping bag/tarp combo for 3 days, no problem. day 4 I start building a celtic hillfort with my swiss army knife.