It's the effect... receiving CD's you've already heard isn't nearly as fun and exciting as getting something you haven't. It's like it's there and you tear away the wrapper to look at it and... that's it. Because you've already heard it and have the file on your computer... I know this feeling well from my Ayu albums and if I can help it, I wanna minimize it as much as possible now and with future releases. 
.... even if it means torturing myself with waiting. 
Scratch that, I just re-read your post and I misunderstood.
I have to wait until the release date because that's when my orders (with FedEx) usually arrives.