After delivery date, buyer gets 5 days to accept, else money is transferred to seller.
Similarly, if non-delivery claim is raised, seller gets 5 days to respond, else money is transferred to buyer.
If claim is made, eBay takes 2 days to evaluate the proof.
If delivery proof is missing, then eBay contacts seller and requests solution. A conference call is arranged if necessary between eBay rep, seller and buyer. If buyer agrees for extension, then claim is dropped, else refunded immediately.
If delivery proof is present, Seller is pretty much sure of getting the payment, but it might take a while for claim to be settled since eBay will try to contact buyer and find the issue.
So, as a seller it is very important to use a tracked courier service and
as a buyer it is important to accept package (sign) only if it is received in good condition