Many people stay in the woods for extended periods of time, so from a gear stand point I don't think there is an issue. With the gear that the average backpacker carries in his pack, anyone with basic experience in the woods can theoretically stay out until that gear falls apart. The main issue (IMO) is food. Being able to gather or hunt enough food is not a matter of positive mental attitude. In the northern forests, relying on being able to gather food is just not realistic. A cup of blueberries (a fairly high calorie food) has 80 cal. To get 3000 cal per day on blue berries, you would need 38 cups or more than 9 quarts of blueberries per day. Most edible plants have even less calories. People who survive in such conditions usually do it in communities and they gather certain seasonal resources that then get used during the rest of the year. This may include gathering acorns or other nuts and grains, or hunting during a particular migration season. It is very optimistic to think that one can just go into the woods alone and hunt and gather enough food in the northern forests to live, no matter how skilled (ammunition supply problems aside). Most of the examples we have of people doing this involve resupply mechanisms that do not come from the forest.