I used it about a month ago to depart Cynthiana, Kentucky into IFR. 
Worked fine.  They actually gave me a longer void time than I requested. 
  Lexington approach was all ready for me.
       David
Dave Butler wrote:
 John Clonts wrote:
 On Nov 2, 12:45 pm, paul kgyy  wrote:
 I've heard some discussion that there is a national number to call for
 a void time on filed IFR flight plans.
 True?  And if so, what's the number?
 I saw (I think it was here) that there is a nationwide clearance
 delivery number, 1-888-766-8267.  Have not tried it yet...
 
 http://groups.google.com/group/rec.a...65d4248984dd78