90 days, but as far as I know listing fees are charged, then only credited back if the relisted item sells the second time (applicable to auction format only, and I don't think it applies if the original listing was free).
If you click relist on an unsold item, it should take you to a page confirming all the details without having to submit the listing, and a note should appear at the top if the listing will qualify for a credit (if it sells).
http://pages.ebay.com.au/help/sell/questions/free-relist.html
