Not really. The program, however, is not limited to first-time homebuyers; you may participate as long as you do not own another home at the time of purchase. I think you are getting the 3 years from the criteria for current NACA homeowners. They must have lived in their home for at least 3 years and have been active participants in the NACA program to be eligible to purchase through the program again.
You can also view with website for further eligibility requirements. Good Luck.