See this link:
http://pages.ebay.com/promo/nofees/
I believe 3-5 day auctions DO qualify for the promotional fees. I couldn't find anything that said they were exempt.
I was trying to search for info on listing duration, but at this time it is 'unavailable'. I think you can shorten your listing time but only within certain gidelines, I'm really not sure.
Read the link carefully...listings are Not completely free! Here's another link as well:
http://www2.ebay.com/aw/core/200708291547462.html