Depends if they are free range or penned. With birds penned 24/7, it's more important to worm than with free rangers who find natural wormers in their forage.
I didn't worm my flock until they were over two years old, and I only did it then because I saw a worm in a rooster's poop. I may worm the entire flock once a year, if that. I will worm the bantams because they do not free range except on rare occasions.
A healthy chicken can and usually does carry a very small worm load. It's when the worms get too much for their systems that they need worming.
If I get back to one large group that free ranges all day, every day, like it was in the beginning, and not just every couple of days, I may back off and worm them every couple of years, unless there is a specific reason for it. Others worm regularly, but situations are different.