I find it pretty hard to keep the game pace slow. There are too many ways to take offense at what the AI does. I just had a stretch of about 10 years of peace in my campaign, and it was killing me. I finally gave in and pounded the Spanish (they were building too many ships, can't have that ).

I find a slow game hurts the King's influence and generals' loyalty. No wars means you can't train your heirs, and generals start getting lazy. After years of peace and a couple of successions, your 2 crown, inbred, unhinged loon of a king is not going to be able to keep things together.