The term Photopass uses is "claim," not activate.
You only have 30 days to log into the Photopass web site and claim your photos; after 30 days, they are deleted - gone, poof! forever and ever.
When you claim them, the clock is reset to 30 days again - you have 30 days after you claim the pics to buy them (on CD or as prints or in a custom album, whatever). 30 days after you claim them, they are deleted.
And no, it doesn't matter when you claim them - 2 days after they are taken, or 20 days after they are taken - when you enter the Photopass card into your account and claim the pics, the 30-day countdown starts.
Some people have heard the number "60 days" thrown around by CMs or by other DISers. The "60 days" refers to the fact that if you wait 30 days till the last possible second to claim your pics, then wait another 30 days till the last possible second before you buy them, that adds up to 60 days.
So, I'm sorry MommyPoppins, but the pics from your May and September trips are all gone already.
You can still use the Photopass cards from those previous trips. The cards are just barcodes with serial numbers that act as an ID tag to help you claim your pics, and they can be used over and over again.
Just be sure to write down the number from each card, in case you lose one. With the number, you can still claim any pics that are associated with the card, even if you lost the card. AllEarsNet recommends taking a digital pic of the back of each PP card with your own camera as soon as you get it, that way you can look up the number while you are inside the parks and view your pics at one of the Photopass viewing stations.