Look on his website for a picture of his Lego Room. About 10 years ago he had custom storage shelves built for his pieces. Probably cost $5,000+ but they are sweet (stacked and on sliders).
Yes, he built all of those himself but he does not keep them built. Each castle gets meticulously researched, built, photographed, and then cannibalized for the next build. At most, he might have 2 or 3 together at a time.