I'm pretty sure the cookie lasts 30 days. I searched the ePN site and couldn't find any indication either so I experimented. I cleared my cookies then went to an ebay affiliate site that I am still developing (discountroombas.com). When I went to the site (which had the eBay RSS feed on it) I had two sets of cookies with the following domains and expirations: discountroombas.com (4 cookies) 6/24/2008 end of session 6/24/2008 12/24/2008 ebay.com (1 cookie) 6/24/2009 I then clicked on a link from the widget and had two more cookies set: main.ebayrtm.com (6 cookies) end of session 6/24/2010 6/24/2009 (x4) ebayrtm.com (1 cookie) <---- this is what you are looking for!! 7/24/2008 Hope this helps.