Well, I'm 60 and I can tell you that it gets less and less exciting until you have your own kids, then grandkids. Children are what make it really magical, and you find yourself doing all kinds of crazy things to keep them believing!
'Fraid so, but it's subtle enough that you don't really notice it until a few have gone by, and by that point there isn't too much disappointment. It's still possible to get excited, especially if there's someone with you who does get excited like a small child (assuming you like the little monsters, ugh!), but for me certainly I don't get particularly excited anymore. Of course, I'm just a grumpy scrooge who tells everyone not to get me anything so it's not the same for everyone
I'm an adult and I still get excited. It's the time of year when I get to see all of my family and old friends. It's not the same type of excitement as when you were a child but still a lot of fun. Also when you have your own kids you'll get excited again because of their excitement. Enjoy your holidays and cherish the people you love!!!!!