Yeah, there are triggers where he does and doesn't appear, but when I'm in one of the parts where he's active and I only have an hour to game and in the first half of that hour I spend a total of 15 minutes hiding from him that doesn't work for me.
I think the threat of him appearing is very effective, the dread that he might at any moment appear, which is why I would have preferred an option to make him less frequent, so that threat is still there without it sucking up so much of the time I have to play.