When you get a Great Leader - can they only hurry production of the current items in production? Or can you save them for an upcoming wonder? The reason I ask is I got one in my last game and the "hurry production" option was available when the leader arrived to a city, but disappeared shortly after and I ended up building an army even though I wanted to get the next wonder to come along.... So, I take it you cant save them? Or am I missing something?