Actually, that is a common misconception that everyone on the disboards seems to have. If you register before you use it, your 30 day time frame to edit and order pics begins from the first time you log in after you take your first pic, not the day the picture is taken. So, if you don't log into your account until you get home and are ready to start making edits, then you are fine. You have 30 days from when you take your first pic to log in and then start your 30 day edit time running. I know this for a fact as I have done the pre-registered card at DL and at WDW and I am one that is always bumping up against the edit deadline so I need that full 30 days once I get home. It actually says this in the tiny fine print on the back of the card they give you to pre-register.
I would highly recommend pre-registering. It means that your pics go directly into your account when they are taken. If you lose your card, you won't lose your pictures. Last summer at DL that pre-registered card saved my behind. I always take a photo of the number on my photopass card in case I lose the card. For some reason, last summer's DL trip was the one time I forgot to do that. Sure enough, we are standing outside Ariel's Grotto waiting for it to be time to check in for our reservation as we were too early to check in, and I drop my photopass card. We had just taken a couple of pictures with Sailor Mickey and I was holding the card and just getting ready to slide it back in the side pocket of my purse. There is a little grate out there on the ground with tiny slits that I was standing next to, just about impossible to drop anything down and theoretically if you drop a photopass card and it lands flat it shouldn't go down the grate. Of all the bad luck, my card somehow goes down perfectly on its thin edge and goes right down that grate never to be seen again. I don't think I could do it again if I had tried. So, the only time I ever lost a photopass card, was the one time I forgot to get a photo of the number on the back. If I had not pre-registered the card, I would have lost the pictures on it. When we got home from our trip and I logged in, all of our pictures were right there in my account and I breathed a big sigh of relief!