I don't grow pumpkins as I work a pumpkin farm every year but at the end I take a 1/2 truck load home for the geese and chickens. I have found the flat deep ribbed pie pumpkins last the longest. Carving pumpkins rot first. No nicks, a stem and never frozen can last well into the new year. I store them in the tack room (unheated), single layer, not touching, off the floor. Everytime I feed one I check for signs of rotting and that one is fed first. Spraying with a light bleach mixture is supposed to extend them so I might try that. It did get below freezing last week so it might be a lost cause but I can usually nurse them along for a month.