Such a good question. -- Excellent too, to hear that Flaming Chickens has healthy birds from pullet eggs. When I was reading up on Chickens like crazy last year, I read that for the healthiest and most vigorous chicks to wait until the pullet's eggs reach full size---which is about a month -- right, chicken experts??
Especially for me, in the heatwaves last summer, I wanted to hatch some eggs as 'insurance' against mortality of my birds and their particular genetics. Since being on this board, I have never heard of any Cream Legbars hatching out sickly. Seems like they either hatch or don't hatch, but not that they hatch out as sick chicks, (or weak ones).