Well... to make an incredibly long story short, I went to a concert in New York (Mastodon), and waited outside for 13 hours in line on an extremely hot day in July. By the time we got inside, it was still a 2 hour wait, and once the concert was over, I could barely walk. I ended up having a heat stroke, throwing up 4 bottles of Gatorade and a ton of bile in a train station, bearly being able to walk, and spending both train rides home throwing up in the bathroom and having to cling to my best friend's shoulder to remain upright. If you know what public train bathrooms are like, you'll understand just how much of an issue that is. I ended up sleeping for almost 20 hours the next day.
...totally worth it, going to another concert in Boston on Friday with likely similar results (In Flames & Between the Buried and Me).