The answer to #4 is probably that the goal isn't to always have ice cream. The goal is to run a profitable business.
Doubling the cost of the ice cream infrastructure to avoid a 25% downtime may not be a profitable venture -- especially if the downtime is scheduled to occur while the store is closed.
Doubling the cost of the ice cream infrastructure to avoid a 25% downtime may not be a profitable venture -- especially if the downtime is scheduled to occur while the store is closed.