dnamertz --
I was waiting to see if anyone else responded
(like Kristin or Kilala -- anyone who did more than one party last year) and answered any or all of your questions before I said anything. Since no one has replied yet -- and the further this thread drops down the page it will be less likely that someone sees it to answer you, I will comment on your questions.
Crowd Differences from One Night to Another: Here's the thing that has to be remembered -- all of the parties sold out last year. (Well, at the very least, all but one party -- the party night right before Halloween -- sold out, and I actually think that one sold out too, but at the last minute.) Not only that, but the parties seemed to sell out faster than they had in previous years, which took a lot of us by surprise.
So -- even though I'm not sure exactly how many tickets Disney sells to their parties -- let's just pick a number and say that they sell 10,000 tickets (which may be way too low, or way too high, but it is only being used for the purpose of providing an example) for each night. If Disney is selling 10,000 tickets to each party, and each party sells out, there can't really be a "
this night was more crowded than that night" type of answer because all of the sold out parties would basically involve the same number of people in the park, give or take last minute-no-shows or whatever.
What could happen -- just as it happens in the parks during the daytime -- is that people in the park congregate in different areas. So, one night might involve crowds congregating in one area and other nights might involve crowds congregating in other areas, which could add to the
feeling of one night being more crowded than another, even if the number of tickets sold was exactly the same.
There are at least a few of us who think that Disney has been over-selling the tickets to the parties, and the parties are all beginning to feel less "exclusive," so my guess is that Disney increased the number of tickets sold last year even more. And, again, all but possibly the pre-Halloween party night sold out (and that night probably did sell out at the last minute) last year.
Treat Trail and Character Photo Spot Closures: I don't think the treat trails and character lines disappear/close a full hour or two early -- after all, people are paying to enjoy those specific aspects of the party so it would be a rip-off if Disney took them away that early. But I wouldn't be shocked if the trails and the character lines shut down a wee bit before party closing. I don't know if they do that -- but I wouldn't be surprised. I just don't think they'd close early enough to make a significant difference. A lot of people hit the treat stations at the end of the party so I assume that most of them must remain open.
I know that characters switch off. At one photo spot you may see Jack Sparrow. Jack suddenly takes a break, so Captain Hook and Tinker Bell step in. I was once waiting in a line for Jessie from
Toy Story, and suddenly she left...but Woody and the Green Army Men stepped in (which was much better for me!). So, as far as I can recall -- and someone please correct me if I am wrong -- the actual photo spots stay open throughout the entire party, but the characters at each spot may differ over the course of the evening.
Main Street after Party Ends: As for Main Street -- hopefully someone will let us know about that for sure. I know that there was at least one treat station set up on Main Street last year, and at the very end of each night the CMs usually hand out tons of candy to guests leaving the park. I don't know if Main Street stays open beyond that time, for shopping. It would be interesting to know.
Fast Pass: I don't know about Fast Pass -- remember, a lot of the lines for rides will be non-existent or very short. Haunted Mansion Holiday and Space Mountain Ghost Galaxy, of course, will have lines.
I hope that helps a little until one of our multi-night party attendees from 2012 speaks up! (Hint hint...Kristin...Kilala...anyone else who went to more than one party last year?)