A good down or winter sleeping bag can be a real life saver in a pinch. It's a good investment that will last you for a long time. Weather you are into down or synthetic (each with it's ups and downs) if the power is cut a good quality bag will save your life. I'd rather have a hot bag than a cold bag, on an investment side I would opt with a good quality bag from Western Mountaineering,Feathered Friends, Wiggy or a know good quality manufacture that people use routinely for expeditions and have good field track records. Eventually you will run out of wood and fuel unless you live in an area that has miles and miles of forest. Then your concern would be to keep that fire going which will go through a lot of wood taking time away from searching for food and water. Just a thought, I know with the emergency bags we have we can stay warm and dry for quite a long time. Also a fire is a life essential as well but will require a lot of wood over time. I try to conserve the fire as much as possible and use it when I need it the most.