Haha! I was just having this conversation last night when the idea of shortening our trip upcoming trip came up due to the fact that more family is coming than originally planned and we don't want them to get "bored."
I use to get the same feeling as you, too. Adding an extra day or two to my trips helps it not feel like it was eons ago when I get home. I think taking a full day in the middle of the trip to do absolutely nothing Disney related for the day helps break it up so it sticks a little better in your mind. We'll go to the Space Center, explore Celebration, head to a mall, etc. Once we even ventured over to Universal for a couple days (bad idea to do that in the middle of a Disney vacation. At the start, sure. In the middle all I heard was comparative complaining. i.e. why did we have to pay for a 'fast pass", why is there no where to eat, why don't they follow a central hub layout
). During the Christmas season, I do like to stay on property for my "off" day just enjoying the decorations at various resorts. But otherwise, a day off works great for me. It gives me a tiny little opportunity to miss it while still being able to be there. That way, when I go home, I've kind of already dealt with that emotion and can focus on the feelings of being there. Then I don't feel as though it was such a whirlwind that flew by so fast that I feel like it never even happened or as though it was forever ago.
I've also stopped looking at photos I've taken throughout the trip while still on the trip. I know that's super hard to do, but I stopped. I don't look at pictures until I'm home now. Then it's a fresher memory for me, because it's the first time I'm seeing the moment while I'm removed from it. I also bring a few "scents" home with me. I know that might sound cheesy, but it works. Every time I smell those H2O lotions in stores, I'm right back at Disney.
And of course, as soon as I get home, I'm making a list of all the new things I didn't get to do or try, and start planning the next trip based on those things so I have something to look forward to. You can never say you've seen everything at Disney World.