I normally promote my surviving catapults to accuracy at the time I get trebuchets because I'm not going to attack with catapults when I have trebuchets. The catapult might not even damage that longbowman he's attacking but with accuracy he can take down defenses like a non-accuracy treb.
In a few games there were barbarians marooned on islands or on the continent but limited to one or two squares by mountains or the great wall. I used them to get most of my siege weapons to 10 xp by continuously attacking the barbarian. It worked better when you could attack with siege weapons from the sea and the barbarian is forced to be stationary and heal 10% so that you can attack him every turn.
In a few games there were barbarians marooned on islands or on the continent but limited to one or two squares by mountains or the great wall. I used them to get most of my siege weapons to 10 xp by continuously attacking the barbarian. It worked better when you could attack with siege weapons from the sea and the barbarian is forced to be stationary and heal 10% so that you can attack him every turn.