First check their feedback and get some ideas how is this sellers history. If it shows this is always a slow one, wait for a while and leave him a neutral feedback. But if you are not crazy about the item you bid, you may ask for refund anytime before they ship it out. By the way, I don't understand why some sellers are so rude, I can never hold others money and delay like this!
Forgive me if l am incorrect but l was under the impression that a seller should ship within seven days unless has a mutual agreement with the buyer before hand or has it on their auction listings that it will take longer.
The same goes with payment from a buyer as a seller cannot go through the NPB process until the 8th day