It really depends on how you drive and store your car. If you typically keep your car garage or under a carport the majority of the time, you can expect it to last between 4 and 6 months. You should note, If you leave your car exposed to the sun for long periods of time, or under a tree while it rains, you may only get 3 months out of the wax.
Also, taking your car through automatic car washes, or washing your car with unsafe soaps will severely reduce the longevity of your wax.