Generally feed till 18 weeks old or the first egg is laid. Then transition to a Layers feed.
Offer Oyster Shells in a separate container after 16 weeks old.
I don't feed a layers feed, I continue to feed a Non-Medicated Starter-Grower or a All-Flock crumble to the Hens with Oyster Shells separately.
I give low Protein treats daily, "Scratch Grains". So I like a higher Protein feed "18 to 20%" than most Layers feed 16%. GC