This Christmas I decided to try and stop that cycle by creating some shelves for his room to display the completed models and while I was at it I created a shadow box to display some of his favorite minifigs.
The shelves are just a wooden box made with 1" pine. This is a three foot shelf so each section is 12" wide and 10" tall.
For the minifig display in the middle I used 1/4" MDF cut to the dimensions of the opening. I then painted the MDF and used Gorilla Glue to affix LEGO bricks to the MDF. The minifigs snap onto the bricks and he can swap them out as he wishes.