In most cases, eBay refund time is up to 72 hours after the refund request is accepted. However, it also depends on the payment method your buyer chose to finalize the transaction:
If they paid using PayPal: The buyer will receive the sum on the same day eBay confirms the refund.
If they paid using debit cards: The buyer will receive the sum 3 days after the moment eBay confirms the refund.
If they paid using credit cards: The buyer will receive the sum 3 to 7 days after eBay confirms the refund, but he may not see it in the account until the settlement date is negotiated with the bank.