I live in a tropical climate. Usually we breed from an incubator between July and November (winter to spring). When you finally get those roosters and start your breeding program, and if you decide to use an incubator, you'll find you'll need to heat their first box, maybe until some feathers start to grow. Bantams may need a bit longer than large fowl. I generally put them into a box for 3 days so I can medicate them with oxymav100, then transfer them to another box for a few weeks. I set eggs weekly so they hatch about the same time.
While I'm ranting, I'll just mention a few points about disease control, JP. I am speaking from experience. My advice is to breed your own chickens, or get them from the same breeder. If you keep spotting pretty ones here and there, your chance of bringing in a disease is increased. Some people have access to vaccinations, but usually those who live near a chicken farm and can use their facilities. For most of us, the expense and number of young chickens you need to have makes this impossible. I have heard it said that live vaccinations can bring disease into an otherwise clean area. That is how they think some diseases have actually spread. If you put vaccinated chickens too soon with unvaccinated, the virus can potentially infect them.
Anyway, we used to have a bit of marek's disease here, a nasty slow death by paralysis. It was only the odd one, but I spent a few days on the tractor and brought in clean soil to cover the entire yard, and that seems to have eliminated it, because mareks can live a long time in soil. There has been the odd bout of something like coccidiosis, but I think the oxymav treatment gets rid of that when they are hatched, so that has been no problem. But the worst disease has been ILT, a kind of herpes virus that kills about 80% straight away (the acute form), then some get the chronic form, with breathing trouble and infected eyes, then the remainder are probably carriers. The only cure is to kill all your fowls and leave the yard empty at least 80 days until the virus dies. I think I either picked it up from some chickens I bought in another town, or from taking my chooks to the shows. A few years ago, it spread through Brisbane show, and the poultry had to be quarantined. I bred a lot that year, and when they were about 3 months old, within 2 weeks most had died. They only get symptoms for 24 hours. The next year, the same thing happened. I called the DPI 2 days before christmas, and they rushed a couple of sick ones to brisbane and had them tested. This was during the avian influenza scare. They gave me the information about ILT, so I had to kill the few remaining and cleaned the coops out with lysol. The only good thing was that the disease is not carried through the eggs, so I was able to breed from a few eggs and keep the prize winning line going. Now my chooks are happy and healthy.
Not all diseases are bad. The other day, a girl brought a hen with worms in the eye. The old fellas dabbed iodine tincture in the eye, and you could see the worms die. You can often treat an infected eye the same way, but sometimes respiratory infections such as ILT actually appear as goopy eyes.