Greek yogurt does have a long refrigerator shelf life, however after a few day the yogurt may begin to separate, this is fine you can simply stir the yogurt. However, the other ingredients you add to the parfait is what will determine how long the parfait will last. Fresh fruit will start to go bad after 3-5 days. While the yogurt itself can be ok to eat for up to 3 weeks. I suggest added your fruit and other topping to your parfait no more than 3 days prior to eating.