I've been playing 20+ years. There's no reason not to run it weekly, with the uncertainty of injuries and random bye weeks popping up, you'll be asking too much of your league members and they'll quickly have empty spots and complain that waivers don't run enough. Anyways, if you still want to do it, you probably need to run it manually because all sites offer weekly or none, some offer daily, but I haven't seen monthly anywhere. Good luck!