Yeah hot glue does set pretty fast and in a matter of seconds it's solidifying and just about cool to the touch, depending on how much you put on at once. Regular temperatures generally aren't the problem, even if it's really hot. The problem is if you leave the parts in a hot car or if they can get heated up in direct sunlight, the glue will soften and seams will pop apart. I found out the hard way when I left my first helmet in a car on a day that wasn't even that hot. It was easy enough to fix, but that's only because I hadn't sealed or painted it.