If yours are like mine you'll notice a gradual slow down. I think people need to remember that a hen, just like a human woman, only has a certain number of eggs to lay in her lifetime. You can add light and "force" her to lay eggs when she naturally wouldn't, but she will stop laying at a...
I'm letting mine go natural. They need the down time. Some breeds never slow down, others slow down a bit, some quit altogether. I believe in letting the hens body dictate what she needs.