A property with a twenty week season should not spend the same amount in November as it does in March. Yet most do, because the account was set up once and left running.
Booking lead times give you the shape of the plan. If your guests book eleven weeks ahead on average, your spend curve should peak eleven weeks before the weeks you need to fill.
Everything else is creative discipline: refresh before fatigue, keep the advert and the arrival looking like the same place.