It's never a good idea to buy a piece of survival equipement without testing it and training yourself how to use it properly and in a timely manner. It's especially true when it comes to shelter/maintaining core body temperature. Please for a peaceful state of mind test and train with your gear.

Dead on Bro. Take one of those emergency bags out into your backyard on a cold Winter night and sleep in it. That is the only way to know whether it will save your bacon if the stuff hits the fan off the asphalt. If you have not done it under normal conditions, you cannot be confident that it will work in adverse conditions, when nothing is working the way it should.

Why would you trust your life to something you have not even tested? To me that is insanity. There is always the possibility that even the best tested and most trusted gear may fail. At least know that it works in the first place.