We have 4 hens. 3 are consistant egg layers, even through winter. we got them all March 2010. One of the hens has never laid for us. we have seperated her out to see if she'll lay. all the others will but not her. She is healthy, eats well and is so very friendly. How often do you end up with a hen that just wont lay eggs ever? should we wait longer or a year long enough to know?