It's quite simple.
Only give a refund when the postal service refunds you. They stipulate the earliest time intervals for when an item can be claimed as lost and take their own sweet time especially for international claims.
Always use airmail as surface mail timeouts can greatly excede eBay and payPal dispute time outs.
Reds are inevitable from lazy and incompetant buyers so let them wait until the postal service machine has processed the problem.
Block them from future bidding with you as soon as they become annoying, afterall you can always remove the block later if all becomes and ends amicably.
Never just refund them due to pestering, be firm, polite and to the point, and as I said before reds are inevitable so why waste time on dozy incompetant and just downright devious buyers.