Once they hit day 18 you meant to stop rotating them correct?
The standard procedure is to increase the humidity on Day 18 so the membrane around the chick doesn't dry out and shrink around it, trapping it so it cannot hatch. Also, you stop turning them at that time. If you are rotating them by hand you can stop after Day 14 if you wish. You have gained the benefits of rotating them by then. If you have an automatic turner it can be convenient to wait and do it all at once.
When they hatching do you just leave them in the incubator?
Before they hatch a healthy chick absorbs the yolk. They can live off of that yolk for 72 hours or more without eating or drinking. That is so that the hen can wait on the later ones to hatch before she has to take chicks off of the nest to look for food or water. I use hours instead of days as days can get confusing. So you don't need to take them out for 72 hours for the safety of the chick.
It is really rare but possible that you can shrink wrap a chick that has pipped but not hatched if you open the incubator and let the moisture out. Many people randomly open the incubator to take chicks out as they dry out and hardly ever shrink wrap a chick. It really is rare. But since I know it can happen, I wait until the hatch is over to remove any chicks unless I have an emergency where I need to open it. If I have a solid reason to open it, I do.
Any advise or things we need to look out for?
You are south of the equator and heading into winter but your temperatures will be mild and your climate relatively dry. Maybe high of 28C (82F) and a low of 12C (54F) for May. Very pleasant.
Chicks need a warm enough spot in the coldest temperatures and a cool enough spot in the warmest temperatures. The way I accomplish that with a heat lamp of to have a fairly large brooder where I can keep one area warm enough in the coolest temperatures but allow the far end to cool off to ambient temperatures. The chicks are very good at finding a comfortable spot. They tend to spend a lot of time in the cooler regions, going back to the warmer areas if they need to warm up.
You need to keep your brooder dry. If the brooder stays wet it can become unhealthy and stink. So if it gets wet, dry it out. If the poop builds up enough that it doesn't dry out the brooder can become unhealthy and stink. So manage moisture and poop levels.
Other than that they need food, water, and predator protection.
What age can we introduce babies to the rest of the flock?
We do this in many different ways. Your set-up and how you manage your flock can make a big difference. Some people wait until the chicks are practically grown to integrate them. I don't. My brooder is in the coop so the chicks pretty much grow up with the flock. When they are five weeks old I usually open the brooder door and walk away. I have a large coop and over 2,000 square feet (185 square meters) in available space outside in a fence. With tighter space this might not work. I do not know what the correct answer is for you.
how often should we change the rooster?? To keep the genes strong??
Good question without an easy answer. It will depend on what genes you have in your flock and how inbred they are. How many chickens total. And how you manage them and your breeding goals.
There are two sides to inbreeding. If you carefully select your breeders for specific traits you can quickly enhance that trait in the offspring. You are basically replacing what you consider defective genes with what you consider superior genes. But by inbreeding you are also enhancing other genes that might be detrimental to thriftiness, health, production, or reproduction. So it is a balance.
If you are trying to enhance certain traits there are techniques for that. Those can take a lot of recordkeeping and work. If your interest is to minimize the potential harm from inbreeding there are methods used by farmers for thousands of years. My father used this method. You can breed parents to offspring or siblings to siblings a few generations before these bad effects start. How long depends on how inbred they are to start with, what bad genes they have to start with, and how big your flock is. Dad would keep replacement chickens for his flock for 4 to 5 generations before bringing in a new, totally unrelated, rooster. This would reset the genetic diversity enough to last another 4 to 5 generations. Dad only kept one rooster but had around 25 hens so the randomness of which hens laid the eggs that were hatched helped maintain diversity. If he had kept more roosters he may have been able to go longer. If he had fewer hens he may have had to change sooner.
One part of this is that you need to select which chickens you keep carefully. If any have traits you do not want do not allow them to breed. Try to keep the bad traits out of your flock instead of enhancing them.
As I said, not an easy answer. Good luck!
