Tardis core- so awesome!! You know you are raising them right when they are building Dr. Who-based lego. :) Transitions are a bit rough, aren't they? Does he have any interest in joining a lego league? It's a great place to find other teens who are in to legos.
My husband is occasionally appalled at the inDOCTORnation going on around here...Ander has a passing admiration for Lego. Based on my experience with a Lego-nut younger brother, I had bricks o'plenty on-hand from the earliest age, but no... He loves the minifigs, and Legoland, and the new movie, and the Lego magazine, but he has never been that into the actual building.