Since this is the 20th Anniversary year, I suspect it may be a little harder to estimate crowd sizes, and most nights you may want to up the guess a bit for that reason. However, since that is a Thursday night (most people have work and school next day), and it's still only the second weekend, I would think the crowds would not be as bad as Friday or Saturday, or later in October. I'm not sure if I've encountered 4 hour waits, but any busy night can easily have a 2 hour wait.
If you can do Stay and Scream, you'll get a good head start on the bulk of the houses, and can kick out 2 or 3 in short order. If the lines get too long, you can also hit the shows (B&T rocks and rules!) and take a more leisurely stroll through some of the scarezones. That is, if your idea of leisure is crazed maniacs jumping out and screaming at you

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