I think Katrina is the best answer, but it depends on what your disaster is. If you live in Oklahoma or Kansas, I'd guess your premier disaster is a tornado. That means long-term survival is probably less necessary as the disaster area is smaller and easier to reach and rescue than the huge flood that New Orleans suffered that wiped out bridges and left scores of thousands in need.

I live in the San Francisco Bay Area, and I expect a major earthquake with Katrina-like results. I plan on survival in place, so I expect a minimum of 2 weeks without aid of any kind. I expect to have fresh water handy, so I have filtration systems, and I expect to have lots of cars around, so I'll have unleaded gas and batteries. That leaves me with food and shelter, and I have that covered in a variety of areas that I can get to just steps from my house if the house goes under. My major fear is fire, as they always follow earthquakes, and I'm downwind of a downtown area and a block full of apartments. Fortunately, the Bay Area has the mildest weather around, so we won't freeze or fry. We've lived here over 10 years and never had an air conditioner in our house, and it's never been below freezing.

I plan on survival in place because I expect the freeways and surface streets to be impassable and the only rail line in town to be unuseable. I also expect all the rescue attempts to be made here, not miles away in some place that's overrun with refugees trying to get somewhere else, emptying out all the stores and gas stations along the way, filling up all the motels, and blocking highways with broken down, out of gas cars and trucks.

My wife and I are ham radio operators with General licenses, and we have HF radios along with UHF/VHF handhelds, so I expect we will have outside communications for whatever that's worth and for as long as we can scavenge working batteries from all the cars in town. We also have 12V lights, inverters, and other gear to allow us to use batteries in a variety of ways.

I have absolutely no expectation that three days of supplies will be sufficient in the disaster most likely to occur in my neighborhood.