20 turns before the next meeting is really too long.

And only one trade allowed per turn is also too restrictive.

I like making several small trades in a session, it's more fun and, it allows more possibilities for the treaties (per example, you can break them later one at a time, instead of all at the same time).

Also, it should be possible to contact a civ during the whole turn duration, and not only for one meeting.

Sometime, I make some trades, and then I need to check something, or trade with another civ, and go back to negotiations with the first civ for several other trades, it's a nice "game of transactions".

The trade phase with other civilizations is a large part of the fun during the game for me, it's really too restrictive the way it's implemented currently.

8 turns before the next meeting would be much better, with full freedom of meeting during the current turn.