What age does a Khaki Campbell stop laying eggs?

[EggHunter_66]

I have a 3 yr old Khaki that hasnt stated laying eggs yet this season, she stops in the winter then startes back up by end of March beginning of April. So far she has'nt laid any. In the bird world she's still young, right? She's not acting sick, eating well...very well like always! I havent even found any nest she's made...very odd?
Should I be concerned that she's egg bound?

 

[Red Maple Farms]

Ducks and chickens slow down after two years. Farmers usually replace their flock after two years because they are no longer economical as layers.