The entire NE and mid-atlantic regions are infested with them now. Some years are better than others, but the reason for the problems in the fall are that as the weather gets colder, they start seeking shelter for the winter, and that means they move indoors on you.
This last fall where I live was less of a problem than the fall of 2011, when I spent most of the winter disposing of over a dozen a day. They tend to gravitate to the south-facing windows on warm days especially.
For what it is worth, they are immune to virtually everything in the "bug spray" arsenal, so you can't kill them in the house that way. I've an orchardist friend who tells me that they are a big problem for him, as during the summer they attack his fruit crops and spoil a lot of his production. He has tried the most potent insecticides the EPA and FDA will allow him to use, and he applies it one day, the next day the ground is covered with seemingly dead stink bugs, and the very next day they are all gone, back up in his trees munching away with renewed zeal, evidently merely stunned briefly.
The official method of dealing with them in the home is to use the vacuum cleaner and just suck 'em up with the hose & crevice tool. They will be unable to find their way out, and eventually die.