Three to five days. If you cut the stem of a pumpkin, the fruit will stay fresh for three to five days. Once you finish carving it, your pumpkin will keep for three to five days (or even two weeks if you live in a cold climate), before it starts to wilt and starts to show signs of decay.
After all of your hard work, it will eventually stop growing. That's not very long when you've put so much time into carving your pumpkin. It's customary to cut a hole in the top of a pumpkin before you start cooking it and stuffing it with stuffing; it is actually the worst thing you can do for your pumpkin — as it will cause it to die. Cut the back or even the bottom of the pumpkin out if you want to keep it from rotting.