I have two white leghorn girls, who are a few months over a year old. Still laying a big ol jumbo egg for me every day without fail. Laid all through winter too. Very flightly girls who scream and flap when I try to grab them up..........but are the first ones to come running when they see me. Treat hounds.
Interestingly enough, I hatched out some of their eggs..........fertilized by my big jersey giant rooster. Kept 4 of the 5 girls (my neighbor got 1) and they are broodiest little birds ever. 2 are raising babies now, a 3rd is broody and trying to sit and the 4th was broody but I "broke her" from it. I had to get rid of the rooster as he turned into the nastiest thing ever.....but wish I had hatched out and kept more chicks.
I wouldn't want a whole flock of flightly white leghorns, but they are definitely keepers in small quantities in a mixed flock. When I was getting 2-3 eggs a day this winter, there were always the two big white eggs there waiting for me. The mixed daughters seem to be a better cross....beefier (chickenier, LOL) birds that are still great layers but also excellent broodies.