There is a broad array of expert advice on cold brewing times. Some say 24 hours, others
18 hours or 12 hours. The facts is that if you cold brew your coffee at 70 degrees for 8 hours, you are going to extract the majority of the solubles from your beans. After that the effects are negligible.
Ultimately, your brew time should work with your shops schedule. You can brew at the end of the day (6;00 pm), and have the first person in the morning drain (7;00 am). This should give you a consistent brew for your shop!
Recently, I have run into people who brew in their refrigerator. Brewing in the refrigerator will produce a coffee extract that is 1/2 the strength of brewing at room temperature. So, one would have to use double the coffee to produce the same strength than if you brew at room temperature.