Joe, can't speak from experience about "prolonged" exposure as the longest was just short of 60-minutes, not all night. I normally keep the tripod in the back of my pickup that has a cover overnight and the temps in Jackson Hole can get very low but then again it's covered.
I'll just say that in all the time I've had the Cube it has never let me down due to any weather conditions. Actually it's never let me down period. Every time I respond to a post asking about the Cube I chuckle thinking about the questions I asked before I went out and spent the money for mine. I also silently thank Jack for suggesting that I do saying if you get it you'll never regret it. It's been several years shooting in surf, sand, ice, snow, mud and I never have.
Don