My son doesn't ask for Lego's anymore, but when we used to shop, I wanted the Death Star, it's the coolest lego set!!!!!!!!!!! We do have the Milennium Falcon and an At At Walker that were pretty pricey, that were assembled and stayed that way. They are really cool pieces.
Try showing him the other star wars models on the lego site, because he might decide that some other set would be more fun. The death Star one is for ages 14+ and is in the Ultimate Collector series so is designed for display and not play.