Ok, here is what I have done. I ordered PP+ and picked up my lanyard on April 3rd. We had photos taken while we're were there ( through the 6th). I waited until May 2nd to claim my photos on the Photopass site (you have 30 days from the date of the first photo to claim), giving the photos the expiration date of June 1st or 2nd, i don't remember which. (You then have 30 days from the claimed date to edit and order your CD.) I then ordered the 15 day extension, giving the photos the expiration date of June 16th.
We took a second trip on May 27th - June 1st (just got back). I used the same PP+ card so that I could wear it around my neck, and also because many of the photographers will take more shots if they know you have PP+. (One took 28 shots at one character visit and another took 30). All of these pictures are claimed in my account the day they are taken, since I am using the same pass number. So, as long as I order my CD prior to June 16th, I will get all of the photos, from both trips, on the CD. All said and done, I will have about 800 photos on the CDs they send me.
If I had taken the second trip a little earlier in the month, I wouldn't have needed the extension.
I hope this helps!
The website with its "14 days prior to the date on the card" was confusing me. I wasn't sure how they were figuring this magic "date". haha
) That was exactly what I needed to know. I'll just make sure I use a new regular photopass card for the first three weeks, and then wait to claim the pics until just before the 30 days so that they'll have similar expiration dates as the PP+ card I'll get for the end of the month. 
