Does brewing hot chocolate for longer hours make a difference? I've been to some stores that offer hot chocolate that has been "brewed for 2 hours". I've also come across the following recipe that instructs to let the mixture sit for 12 hours. What does this achieve? What actually happens?

Ingredients:


500g whole milk  
100g 35% cream 
140g Inaya™ 65%  
40g sugar  
20g Extra Brute


Method:

Bring the milk to a boil. Pour over the cream. Add the chocolate, sugar and cocoa powder. Let sit for 12 hours. Serve at 60°C.
Cacao powder is not very soluble in water, so I'm gonna go out on a limb here and guess that the extra time allows for the cacao to incorporate better into the liquid.

The recipe includes actual chocolate nibs, but after it's melted into the milk / cream there's no extra flavor infusion by keeping it for a longer time.

12 hours sound like a lot: if you keep the mixture cold, it takes longer to dissolve (but not that long); if you keep it warm there's a risk of spoiling the milk. I can't think of a benefit to let the drink sit for such a long time.