When will Mother hen be done?

[Cheerful]

I have a mother hen raising 6 chicks. She is doing a great job, and they have been free ranging together since day one. The chicks are eventually going to go to a friend of mine. They are nearly 4 weeks old. Have been doing some reading to find out when I can expect her to be "done" with the chicks. My preference, of course, is to let her decide, though I did read some people saying the mother stayed with chicks for MANY weeks - like 16. We have 6 chickens already and don't have the space to allow them to grow to basically adult size so I was hoping that maybe she might be done around 8 weeks....? Thoughts? Also, at that point, would it be horribly cruel to take them from her if she still seems inclined to look after them? (the mother in me cringes! ) Another thought I had was to see if my friend would take the whole brood (mother hen included) until she was totally done mothering and then get the mother hen back, though I'm sure this might be stressful in it's own way to the mother hen. Or, and this may be totally off the mark, remove 5 of the chicks and let her keep one to look after? (but hey, missing five of your babies is probably pretty stressful and I'm not sure leaving one would help much.)
Ideas?

 

[McGobs]

When you bought chicks the first time...they were most likely day old chicks right? They can be taken at any time and be fine I would imagine. This past week, I had a silkie that was raising 4 chicks go missing. The chicks are only 3 weeks old, and they seem to be doing just fine right now.

 

[Cheerful]

Thanks - I'm actually not really worried about the chicks doing OK, more the stress on the mother. And I suppose the stress on the chicks. When you get day olds they are most likely hatched in an incubator, and have never known a mother so it seems a bit different.