No need to remind buyers that they need to pay. When they win, they get a "you won" email. They get an invoice from the seller, if the seller sends one and then they get a reminder from ebay to pay. So basically they get 3 reminders to pay. Then if by day 4 they still haven't paid, you start the unpaid item dispute which would be their 4th reminder that payment is expected.
As the non payer to your blocked bidders list. and set your buyer requirements in My Ebay, Account, Site Preferences to block bidders with 2 or more unpaid item strikes in the past 12 months.
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Non payers should get unpaid item strikes and be added to block bidders lists. Period.