I have seen many people do not put thermal racket cases over their rackets as they just stuff them into their bags. I don't mind doing that, but since I have to carry my bag through Canada's harsh winter temperatures, I might have to put thermal cases over each racket. Is this really necessary? Can I just stuff all of my rackets into one compartment of my bag and not put any thermal cases on each one? Or do I have to put thermal cases over each racket to prevent the cold temperature (ranges from 0°C to about -20°C to -30°C (thats 32°F to about -4°F to -22°F)) from damaging my rackets/strings? Any suggestions?