I have a silki mama who is free range, she panicks if her babies aren't near her (she only has 4) but its also winter here so they need her more for warmth right now. She has been an extremely attentive mother, but I also have heard thats part of the breed. This is the first time one of our girls has hatched so she's all I can go by.
The older the chicks get the less they need mom's heat and will wander farther and farther. It is usually closer to 6 weeks when the hen stops keeping a close watch on them. Some hens are better than others at keeping watch.