I have to disagree with Finsky here, I have had one of my queens for comming on 2 years and, she still has the best brood pattern of any of my hives. Her hive is already in it's build-up and, upon last inspection, had a broodnest already spread out to 8 frames, with three of them filled completely top bar to bottom bar and side bar to side bar. I only see it necessary to replace my queens if they show signs of disease, develop a poor brood pattern, or become too deffensive. In most cases, I just let the bees establish their own superceadure queen if it comes to that.