Anne you only have 30 days to claim your photos from when they were taken. So if you wait a couple of months and then go to photopass and enter your card number the photos will have gone.
After you have claimed them, they are then are only available to alter for 30 days and then must be added to a CD by then. You can purchase 7 or 15 day extension for your claimed photos if the 30 days isn't long enough.
I almost missed my cut off once

I had done a photobook and hadn't saved it, then they expired the next day (this was before you could buy an extension).