Recirculation of Urban Legends

I just got another e-mail referencing Ben Stein’s Christmas comments and had to pause to reflect on the fact that this is the third year that I’ve gotten e-mail with this.  The first one was sent to me back in mid 2006, with another round in 2007 and now one in 2008.  True, the seasonal nature of this particular legend means that it’ll continue to circulate in the later months of every year, but I wonder what the half-life of such a legend is.