"No hard Innings limit" =/= In the rotation through the playoffs
Horton is going to get paused or slowed down at some point. There's not a hard limit, so it's not some Strasburg situation where Horton hits 120 innings and is immediately shut down, but they definitely have a realistic range in mind and will take proactive steps to limit him to roughly that range.
Expect either an IL trip at some point, even if its for something flimsy, or a transition to the bullpen. Which one they go with probably depends on how well he's pitching.
And every word above applies to Brown as well.