Helloooooooo
My Princess Half time was 3:03ish (2011)...about a 13.7 minute/mile and I stopped for almost every character. I ran a half at home a few months later in 2:35, so character stops added almost 30 minutes for me. Plan on the 6th mile being your longest - it's the one that goes through the Magic Kingdom and where you'll find the most characters. Lines for rare characters are longest, as @
Kristia said, and they are also longer in the earlier miles of the race. When you get toward the end you'll find that almost no one will be stopping for pics - it's just about surviving and making it to the finish by then. The lines should move quickly...there are no autograph books and there are normally 2 character attendants at each stop - one taking the current picture and the other getting the next camera ready. The one at the bad of the castle will always be long...normally that'll be a prince/princess pairing switching out with Royal Mickey and Minnie. Oh, AND...make sure to keep your eyes peeled at the finish. There are normally characters there that will stop for pictures and almost everyone else will pass them. It's a super great way to get a picture with the finish in the background, and the characters will be in royal attire. Like so:
Do keep proper race etiquette in mind: you may see a picture you want across the course. Be aware of who is around you and try to give notice that you'll be crossing the course or stopping for a picture, otherwise you may end up slamming into someone. Not a very magical experience.
Personally, when I train for these things I don't do it with a goal time in mind. I just try to aim to get in good enough shape so that I can complete the distance within the allotted time while feeling great and being able to take it all in (no record-breaking times here). There's nothing like running in Disney...you'll love it.