A pet point is a point obtained when the player has a Legendary pet summoned. The player gains one pet point every 60 seconds. Pet points count as the 'time' it takes the player's pet to grow up. There are three stages - baby, adolescent and adult. It takes 900 minutes, or 15 hours, for the pet to reach the second stage of life, and a further 1500 minutes, or 25 hours for the pet to reach adulthood for a total of 40 hours, assuming the player never interacted with their pet for the entire time. Any pet points received while within an in-game menu (such as the Grand Exchange, or any store) will be received after the player exits the menu.
Additionally, a pet point is added to a reserve for every minute that the Legendary pet is active, up to a maximum of 30 points. After half an hour of active in-game time, 30 pet points will have been added to the reserve, assuming that its initial value was 0. The reserve pet points are added to the pet point counter once the player interacts with their pet and initiates an emote. If this is done before the maximum of 30 points has been added to the reserve, the current number of points is deducted from the reserve and added to the pet point counter. Subsequently, the reserve is set to 0. Because of this, the best way to take advantage of this mechanic is for players to interact with their pet at least once every 30 minutes. As a result, a pet can reach adolescence after at least 7.5 hours (900 / 120 (points + reserve each hour)), and adulthood after at least 20 hours (2400 / 120).