There are a couple of tricks to having year round egg supply.
First freeze extra eggs for baking or scrabled egg dishes, when you have extra. My egg production in SD slows down in the winter, as I don't add artificial light, however, I generally get a few, enough for our eating needs. In the summer, I get high production, so by freezing them, I use those for baking and cooking for the large crew when everyone is home. Keeps me from running out of eggs.
Multiple age flock, young first year birds tend to lay smaller eggs, but do lay through the first winter, IF they are laying before winter. Last year, I had late chicks in June, and they did not start till January, but from then on laid well.
Adding artificial light, but only do so if your coop is properly wired. Makeshift wiring causes lots of coop fires, really not worth a few extra eggs.
Hope this helps.
Mrs K