My brother Dave and I were going from Hamilton to Port Hope one cold winter night and decided to stop and watch my son, who was playing at The Horseshoe Tavern in Toronto. We left my '62 D-21 and his 72 D-18 in the trunk of my car. (No lectures please. I know better but...)
We took the guitars out of the car in Port Hope and left them in the cases all night. In the morning, when we opened the cases, Dave's guitar's lacquer was covered with tiny cracks. Mine had always had these cracks and I noticed no changes to my guitar. Dave was devastated, but almost everyone who's played the guitar before and after this happened agrees that it sounds much better since the crazing in the lacquer.