An uncarved pumpkin can last up to 12 weeks if it was healthy when initially picked. Also, the pumpkin would need to come from a field where diseases are controlled.
When initially picking a pumpkin, always look for a sturdy stem. A weak and flimsy one is usually an indication that it will soften and rot quickly. Also, make sure the pumpkin is free of spots and visible damage. When storing the uncarved pumpkin, do not put it in direct contact with any sunlight. This will cause the pumpkin to rot quickly. The ideal temperature range is between 50 and 55 degrees Fahrenheit. If temperature goes lower than this, the pumpkin's life span can potentially be cut in half as freezing conditions damage the pumpkin's plant cells and cause early rotting.