You could always call the company, ask to talk to the HR person and let them know you applied at such-and-such time and were wondering how long they keep applications on file. Then, reapply a month or so before they would pull your app from the file.
Every company is different. Unless you call and ask them, you have no way of knowing how often you should apply. And, calling to ask will also put your name in their head again. Who knows, maybe you will get a call for an interview shortly after that.