4 days and 1 minute is my limit. Do NOT send an invoice because the clock resets and the buyer gets an additional 4 days to pay. This is a very dumb move on ebay's part. As soon as you can cancel, go ahead and cancel. There is an option to relist the item too at the same time. So if you want it to list at night for example, then wait until the time that you want the item to restart.
The buyer knows that they they need to pay. No need to remind them. They see an email every morning when they open ebay. On a tablet, there is a red dot indicating that you paid, you sold something or you got an email. They know.
