It's up to you. Send an invoice promptly.
You can open an Unpaid Item Dispute after 4 days (96hours) and close it 4 days after that if the bidder has not paid. You will get your FVF fees back and the bidder will not be able to leave feedback.
Do open the UID when you are sure your bidder will not pay. Or even just to remind a slow payer.
Note that if your bidder paid through Paypal by echeque (from his bank account) it will take up to 10 days to clear, but he has technically paid.
Also once the payment has cleared, PP will hold it against your good seller performance for up to 21 days, again prompt shipping is important here.
Use PP shipping labels. If the payment has not cleared , you won't be able to print it. That's protection for you. If it has cleared you will be able to print it and the cost will be taken from the Held payment.
The Hold is annoying but all new sellers go through it.
