I have GrandPrix ones. Been riding them as cold i usually ride, and dont feel them colder than Palaus, -20 Celcius.
They should last longer than norm thermos.
Molding, shells dont form due recommended temp in real is less than 100C. I use also heated boot bag so i warm them every day to 60+C, it is nice to put warm boots on on morning, and that takes care also that they are dry.