I didn't like caravans either, at first. Looked useless and annoying, kind of "sheeesh bahh"! But when i discovered what amount of gold it could pay, i began to be very interested to it. But strangely, i don't remember to have use it that massively, when i didn't play that often since i beat Divinity by far and rushed the sky at the score... Anyway caravan trade was quite hard to set: it needed a long peace, and it was many efforts (production, prospecting, escorting, ingeneering, treaties, etc...) what were not always rewarded. In civ3 trades are broken when they have to and this is the rule... war goes ahead of trade. I for now expect a reputation hit when i betray one major trade like 120 gold per turn against one knowledge and then declare war (in the same turn of course, talk about such a straight rapt) but i usually don't pay attention to more common luxury trades or exchanges when it comes to declare war, neither do the AI, and it seems to be quite good like that.