Generally, for a better deal at Ibague Airport it’s recommended to book in a timely manner (to save up to 74%). Cheapflights recommends you book around 53 days prior to your pickup date. Booking as early as you can also increases the likelihood that you’ll get the ideal car.
Typically, how long you can rent a car for depends on the inventory of the supplier. For Ibague Airport however, it is certainly possible to rent a car for an entire month.