My problem is my son looks at the sets and says, "Dad! Dad! There's a brick I don't have in that set! You need to buy me the set!" But yeah, he builds a set

My problem is my son looks at the sets and says, "Dad! Dad! There's a brick I don't have in that set! You need to buy me the set!" But yeah, he builds a set by the instructions once, lets it stay together maybe a month, and then it's just parts going into the bins of bricks, to be endlessly remade into whatever catches his fancy.