There is no requirement that you hold it for a specific amount of time. If the property was appraised at $5000 or more and you signed Form 8283 (the apprasial summary) and if you dispose of the property within three years, then you must file Form 8282 with the IRS within 125 days of disposition and give a copy to the donor. For more information about this topic (including special rules for automobiles, conservation easements, and other specific types of property), see http://www.irs.gov/charities/contributors/article/0,,id=182838,00.html.