You'll have noticed that any polls on this board remain at the top of the topics list. They're made "sticky" so that even if no-one's voted for a day or so, in an effort to get the biggest response, they'll still be up there and get noticed by folk who aren't on every day, and don't go through each and every post.
They'll be "freed" after a week, as it was felt that this should be long enough to catch most folk's response. If you've closed off your own poll after a shorter period than this, that's when it'll be liberated.