It really is more about the conditions under which the games are stored, than how cold it gets. The biggest enemy is temperature fluctuations, rapid changes will cause way more damage than if it just gets cold. Due to necessity, I've had games stored in a large, 7000+sq ft, unheated warehouse for the past 8 years, have only lost one backglass and that was because of a leak that caused moisture to get into it, otherwise no problems. The key is that because of the size of the space, it doesn't rapidly heat up or cool down.