I always quit the game during the last 4-6 months of an expansion. I mean by that point I already have full heroic raid on farm (don't really care about pushing mythic), have all the transmogs I wanted, am wrecking noobs in pvp, and I find myself basically just raid logging, and I don't consider raid logging to be a serious reason to keep paying a sub, so I just quit and then come back during the pre-patch.