I love the idea of living high in the trees, but in reality, it poses some serious health dangers and logistical challenges. A shelter like that would be expensive and time consuming to build. You would need lots of high quality lumber, hundreds of large nails or screws, Ladders, lots of wood working tools, ropes and harnesses, healthy strong trees, good growing conditions so that the trees can heal and not die of disease, and sound architecture designs, and thousands of hours of labor.
From a survival perspective, when you are high up like that, you are more exposed to the wind, rain, and sun. This would not only make living conditions more difficult, but also wear out your shelter and equipment. During a high wind storm, there is a possibility of branches breaking above you and damaging some part of the structure. I think that a treehouse would require a lot of maintenance.
You should also consider how difficult & hazardous it would be to constantly move yourself and supplies in and out of the treehouse; especially during icy conditions and at night. (or drunk) Most of a person's daily routine takes place on the ground, so having to climb a ladder to access your shelter and possessions would require a lot of energy. In a wilderness self-reliance situation, you want to conserve as much energy as you can and avoid taking unnecessary risks.
I think the treehouse is a cool idea, but it would definitely require a lot of forethought and planning to work safely and effectively.