Julie, this is a great question. I, personally, love
Disney's PhotoPass+ for several reasons. The first one is that you can add attraction photos such as those from Twilight Zone Tower of Terror or Splash Mountain, which you can't do with the standard PhotoPass.
Another feature of it is unlimited amount of photos that can be added to the card. So, if I have one of these cards, I take full advantage and most every time we see a photographer, we take advantage. Each photographer has different vantage points even if they are around the same area! It's hard to judge how many photos you would have, but with 8 days and all the parks, I think you would get tons of photos, probably more than you would ever expect. I have come home in the past with around 75-100 pictures.
If you are dining at one of the locations that uses the PhotoPass+ for your character dining, this is yet another great use of this service.
Don't forget to ask the photographers about Magic Shots. This is where you pose a certain way and when the photo is taken, a special image is superimposed onto the photograph to make it even more magical!
So, say cheese!
~Allison L