I allow 7 days for payment and state this clearly in my listings. On the 3rd day after the end of the auction, I send what I call a 'courtesy reminder'. This usually results in pretty prompt payment or at least communication from the buyer. I know that ebay also sends out payment reminders to buyers but I'm not sure at what point.
After the 7 days have passed, I wait 4 days and if I still haven't received payment, I open an Unpaid Item Case. This usually does the trick.
I've come to realise over the years of selling that people's lives are complicated and lots of legitimate problems arise in their lives that dictate against paying on time for items they've won on ebay !!
As a seller, I've occasionally had to send out apologies to buyers of my items for not posting quite on time, due to issues in my own life.
I try to strike a happy balance between tolerance and understanding and preventing my business falling in a heap because of non-payment.
I always hope and usually receive the same tolerance from buyers.
