If i owned a 911 think heated storage should be considered if practical. Seems to minumise storage aging to some extent in my opinion. You will not even have the condensation problem inherent with unheated storage. (everytime car pases through freeze point it collects moisture and dries out) Just great for electrical switches and body metal. Still better than putting them through salt by far though. Cars I keep in heated storage seem to be about as I parked them years ago in some cases. Unheated storage is another thing. I fully realise in some circumstances and localities heated storage is just too expensive or hard to get. Just my opinions.