We don't keep cocks separate from hens unless the cock is running the hens around making them crazy trying to mate ALL the time.
Some of this seems to be breed dependent. My Dorkings are incredibly mellow roosters while my Ameracaunas are more assertive with the hens. My flock free ranges sunrise to sunset and my hens don't seem bothered much by the males. It may be true that my flock isn't meeting it's full potential by letting the hens and cocks range together but it's what works for me in consideration of my goals and resource limitations.
I do appreciate the knowledge shared here and your experience has helped me greatly in my flock management.