Once you get powerful enough they tend to sit there denouncing you for hundreds of years and not declaring war, but it does make further diplomacy pointless after a while. If you even prosecute a war that was declared on you to the point of taking someone else’s city they get pissed off for a very long time. It’s really quite stupid, especially in pre-nationalist times in which everyone was warring on everyone else without these mysterious multi-thousand-year grudges.