I open an unpaid item case as soon as Ebay lets it happen, which is normally 4 days and one second after the sale.   No playing around in my case,  you don't pay,  you don't play.

In my other business, an invoice reminder threatening the debt collector goes out exactly 4 weeks and 1 second after a delinquent client fails to pay,  I withdraw services,  then promise to come back once paid,   but never go back again.  No second chances,  no need to be nice.