One of the powerful benefits of juicing your own juice are the live enzymes there in the juice that tend to die off after 15 minutes. So it's best to just drink the veggie juice and only store the fruit-based juices at the very most.
How much you drink is totally dependent on how much other foods you're eating, what kind of juice, whether you're fasting, your body type... even the weather! :)
As a general rule, it helps to mostly only juice veggies but actually eat fruits so you keep up your fiber intake. :)
I myself drink at least 8-12 ounces most days, but I don't eat much. ;) I'm just 5'2".