<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by DrGiggles:
If you were to achieve Platinum/Gold status through the Challenge...could you then take the challenge again once you went back to no status? My impression is that the answer is no, but I have heard from colleagues that it is possible (they have done it themselves)</font>
The official stance is "no".
However, AA appear to have no system for tracking whether you've challenged in the past so in effect you can do it multiple times.