I usually stop buying starter once the chicks are big enough to leave the comforts of our house and move to the coop brooder...3-6 weeks depending on weather. Once they go out I start feeding the entire flock a multi-purpose feed like Flockraiser. I have also used a higher protein turkey grower and cut it with scratch to bring the protein to something around 20-22%...usually 2 parts grower to 1 part scratch. My existing laying flock seems to enjoy the change for a few months too. Then about now, when my pullets are around 16 weeks old, I let the flockraiser run out and start purchasing lay pellets for the rest of the year. I will generally purchase a bag of scratch to feed sparingly if we have a really cold spell in the winter, just for a bit of entertainment and variety during those cold, dark winter days. But they stay on layer until I bring the chicks out again in the spring.