I recently made a chocolate souffle for the first time and it came out pretty much like I was expecting: slightly gooey middle, a crust on top, fluffy, risen to a little less than double. But after 10-15 minutes they started deflating, until around an hour later they were back to the size when I put them in the oven. They became a dense mush. Is this supposed to happen? Some reports say that proper souffles only deflate a little, while others say deflating is supposed to happen. Which one is true? 
A soufflé is simply a hot air balloon. It stays up as long as there is hot air trapped inside it. Your 10-15 minutes sound reasonable, although it is a gradual process and starts as soon as they are out of the oven. There are tons of kitchen lore about non-falling soufflés. These are either wishful thinking, or marketing trickery. The laws of physics cause a soufflé to fall quickly. 