We were told by a CM that WDW unofficially roughly celebrates the 12 days of Christmas beginning Christmas day (the last day being the 5th of January) and that decorations come down on/by the 5th of Jan. We've been the last three Christmas/NY seasons and can tell you that as of New Years day you begin seeing/hearing some changes as some deocrations come down and some music changes back to the regular stuff. The last 3 years we've gone to bed on the first Friday in Jan with all decos still up in the hotel lobby only to wake up the next morning and find everything back to normal. Must be magic!