I'd say a minimum of 4 hours in balls, I'd probably do 16/8 or 12/12 depending on my schedule and when it's going to be eaten. When you ball you tighten the gluten and it needs to relax again, too short of a timeframe and it might be difficult to stretch, too long and it might lack elasticity. I'm sure that there are many other aspects to this though, but then you are entering expert territory.. You need to find a balance that depends on how the dough was made, how high the hydration, how long and at what temperature you are fermenting, etc..
At this stage you are setting up the conditions for having balls that are nice and easy to open, but also not too extensible, and that are being able to hold the toppings well without deforming. It probably also influences the structure of the final cornicione.