I know people breed for different reasons and I am new to it all myself (chickens for 5 years), so this is a investigative post rather than a snarky one!
Having picked the brains of several old poultry men, I was told by all of them to not breed from pullets-or not ones less than 12 months old at a push and not to hatch large fowl too late in the year. Breeding from young pullets means diminishing returns wrt small chicks from small eggs and if you're breeding for egg production, by rights you should breed after a complete season (including the winter) so you breed from the best layers.
I've bred from 12 month old pullets and hatched end of June, which I considered pushing it. I couldn't be doing with chicks/growers in the winter anyway, running lights etc I prefer them out at 3/4 weeks if possible. This year I am only breeding from hens that are after their first/second moult and I know the laying capabilities of all of them and everything will be finished hatching by end of May (partly because I had a period of no eggs while they all went through the moult lol so want some POL before xmas next year). the 2013 pullets will not be bred from until 2015.
Does this matter with the hybrids do you think? I won't get hybrids again, I find them not particularly hardy and fairly unreliable after their first moult, the purebreeds lay less maybe but seem very tough and lay better in their 2nd and 3rd years.