Hello
We were able to do this... My wife and i had 5 days left of our 10 day no-expire. I called and upgraded to the PAP. We were at WDW in May, and upgraded in July....not sure if the timing had any bearing on this.
Hope this helps.
ps. Sorry, i don't remember how much more cash we needed to upgrade, but we went to the PAP because we still had all 10 of our "extras" available for use that we paid for, and wanted to take advantage of the waterparks.
Mark