There is no specific time limit. However, Apple will let you know when an item you ordered is available for pickup. The item can be picked up then without waiting. If go to pick it up at a later date, you may need to wait.
Regarding this, can I cancel preparing to ship order on Apple?
So long as your item is not in Preparing to Ship or Shipped status, you may be able to cancel an item or the entire order online.To cancel an order or item, visit online Order Status (Opens in a new window). On the Your Orders page, find the item you want to cancel and select Cancel items.
Also to know is, why is my payment on hold Apple? Apple requests an authorization, which holds the funds for the full or partial purchase amount. As Apple prepares your items, authorized funds will be unavailable and may display as “pending” on your credit or debit card’s online statement.