Why do you have to constantly renew trade agreements? Wouldn't it be better if once you got a trade agreements they just remained untill ended for some decent reason like you got to war with the race or whatever? Why is it trade agreements become so hard to get once races start going to war? I can understand not being able to trade with those you are at war with but why not others?

I know its a pain isn't it? i liked them in Moo 1&2 where they were a permenent thing untill you either break them off or do something to make the other race cancel it.

They are probably better balanced in terms of gameplay, but it is a pain, because you really have to make sure you have the liquid cash on hand in order to make the trade deals.

I will usually even pay some or most of other races part of the deal, because it's worth it in the long run, and it's a really good way to make nice diplomatically.

I actually like them better as a game mechanic this way. You are investing a significant sum of cash up front in order to recoup more over time - but not forever. The fact that you're willing to do this makes the dippy bump acceptable - sneakiness aside, you are essentially saying "I not planning on attacking you anytime soon". Ditto for research agreements.

I use the 20 turn expiration as a reminder to check for tech trades. :)