What thickness did get? I've been thinking about replacing our own spring mattress with a Gel mattress but haven't decided on what thickness to get. I'm actually hoping to go with maybe a six or even four to give some additional overhead space.
Oh, and for your question, it would be good to mention your location. Here in California I would venture to guess that it would not freeze on how (do they even freeze?). Somewhere North in higher altitudes who knows.