Unfriending Etiquette

I'm usually not too strict and generally don't drop people until maybe a month or two. I have a full friends list and plenty to visit, and who visit me. I'm a little more strict during events, especially if when there are goals to meet and a limited time to do it. If I have neighbors who don't seem to be playing it and invites waiting from ones who want to, I trade them out after a couple days.