I have some hens I got for a gift from my grandparents. I've had them for a year now, and they were older hens when I got them. They aren't putting out many eggs and its's costing more to feed them than the eggs they are putting out. Plus it seems like I will have to invest in more expensive feed if I decide to use their eggs for hatching eggs. I don't know how old they are, but they are looking a bit ragged. Is it time to cull them or should I let them keep on? And what is a average life span that you guys let your laying hens live to?