Yes, I think if you have a 5 night reservation and you want to change it to a 3 night, they won't just turn your 5 night reservation into a 3 night anymore. They will check to see if there is a 3 night reservation in the inventory. If there isn't, you can't change. you would have to cancel and rebook (and what you want may not be available) because they want the full 5 nights released, not just 2 of them. So if you have a package and you are doing any of this within 45 days, you have to be careful. Also, you might lose a timed discount if it has since expired.