The exact cooking time is hard to pin down in a number. You want to cook the mixture until it resembles runny oatmeal and a good amount of the liquid is absorbed by the rice, but there’s still some liquid in the pot. (You don’t want to cook it until all the milk is absorbed.) The rice pudding will thicken up as it stands. If it’s too stiff after it cools, you can thin it out with a splash of milk or cream. For non-dairy people, I’ve made this with rice milk and it works well, although the pudding will be decidedly less-rich. Using come coconut milk would probably add richness, if you want to use that in place of half the rice milk. If you don’t have vanilla bean paste, or if you prefer, you could use a whole vanilla bean, split lengthwise, in place of the vanilla bean paste, which you can add in step #1. (In case you’re wondering why I add a bit of vanilla extract, whether using vanilla beans or vanilla bean paste, I find that vanilla extract adds a more rounded vanilla flavor, even if using a bean or paste.) If the pudding is too stiff or thick once cooled, thin it with a bit of milk or cream, to bring it to the consistency you like. I like my rice pudding with this amount of sweetness, but you can reduce the amount of sugar to 4 tablespoons in step #1, then add more when the rice pudding has finished cooking., to suit your personal taste.