How long should a chicken lay?

[chicken cooker]

This question has probably been asked before many times but --- how long should chickens lay before they go to the freezer? What considerations determine how long they lay?

I have 48 birds; 10 have been laying since May, 25 since August (they are now 5 months old) and another 10 are just starting to lay now. The remaining 3 are juvenile "strays" that just roam through the barn. They will likely begin to lay before the end of the year.

thanks