At the extreme temps, how gear works (or doesnt) in concert with other pieces becomes the primary consideration in the testing. Some items complement each other well when used together. Others not so much. How different pieces affect the performance of others and whether the combination of all is optimal is the purpose of the testing. I spent one winter in my backyard testing various configurations of items. One will learn intemately how each piece functions alone and with other items. Knowledge is the goal, then you can adapt to various conditions. Often people will say item x doesnt wirk, when the reality is is doesnt work in conjunction with another piece of gear. It is a systems approach, not an addition problem.