Peace Treaties should stand.

I signed a Peace Treaty with a person so I could focus on a bigger enemy. Next turn the jerk declares war on me, takes my capital and I am screwed. An Alliance I can understand, but I think a Peace Treaty should stand like it or not. If not that It should at least remain intact for 8 turns.

That's what peace treaties are there for, peace between two nations so they can divert forces and resources to take out another or several enemies.
And that's the thing with peace, peace never lasts, sometimes you can't even expect Alliances to last.
If your enemy has no other opponent to bother them and you're still fighting they will sense your weakness at it gives them an advantage, so why wouldn't they exploit it?
This is about war, one cannot be a jerk for for declaring war after peace, and for the sake of the game peace should last for as long as one part think it is smartest.
One could request a peace treaty for a certain amount of turns, I would support that suggestion.