Within what time span, is a buyer expected to pay?

[kingelectra]

I recently sold an item on eBay, but after 48 hours the payment has yet to show up in my PayPal account.  I was thinking that sold items were to be both paid for and shipped within 48 hours as a rule.  Is there some guidance someone could provide on when it is legitimate to assume you are not getting paid, a case needs to be opened, and ultimately to relist the item?  Thanks in advance for your feedback.