@Bryan508 taking @Inna22's suggestion even further, you could also have a separate listing for the apartment alone, and only open it for last-minute bookings. We find that our smaller cottage is easier to book than the big house; lower price and cozy space attract young couples. The house tends to book farther in advance, for larger groups, and the umbrella listing very far in advance, for things like weddings and family reunions. So you could, for example, open the umbrella listing one year in advance, the house-alone listing three months in advance, and the apartment-alone listing one month in advance.
Whether this makes sense for you depends on the specifics of the property and your market, of course.