I actually don't leave the frames hanging because of the cold air surrounding them.(I can hear Lynn now: "They should be able to take the cold...!") but I put them down especially when the winter sun is shining somewhere else from where the rack is. There's windows and glass doors everywhere so can't lean rack just anywhere. Maybe I will try hanging them longer in the winter weather, but the taking on and off and back on and off because the sun moves is tiring so I leave it where I know the sun will hit the next day.
Greg, I noticed the sensitivity of the hairy semps and just plucked the majority of them out of my semp bed and put them into a flat where it is not as exposed to the elements: rain, summer sun, winter cold. We had a lot of rain right before the cold temps hit and I don't think the soil dried out too much. I've counted 31 semps lost from rot. Though our rain doesn't compare to what Lynn has described at her semp paradise...
