I believe meat birds need to be harvested at 10 weeks. My wife wants to start getting Cornish broilers, so we've talked about it, but haven't committed to it yet. For me, it sounds like a very busy day butchering and cleaning chickens that I would rather spend doing something else. I'm also not seeing the cost savings compared to buying them at the store compared to buying the chicks, then the cost of feed for 10 weeks, and a full day of labor cleaning them.
In my experience, the first eggs tend to have super soft shells. After a week, the shell gets harder and they don't break as easily on you. I've had them crush just by picking them up. They will lay pretty good as long through Fall, then slow down in Winter, then pick back up again in the Spring. Average is every 30 hours they lay an egg. So you might not get as many one day, then extra another day. It's never going to be the same every day. After 2 years, they slow down. By the time they are 5, you are pretty much done getting eggs.
A chicken that lays eggs is almost worthless to eat. They just don't have very much meat on them, and the older they get, the tougher the meat becomes. Butchering roosters is also pretty much worthless if you wait past 10 weeks. It takes about 4 months for them to turn into the devil. We always wait for that to happen because we're always hoping for one that isn't pure evil. It happens, and we have a few that are really nice. But I've killed hundreds that where horrible. We've tried pulling the breasts for dog food, but it's not really worth the effort. Better to just shoot them with the 22 and dump them in the burn pile.