If you have a million nukes, and I have a million and 1 nukes, does it really make it my domain? 
Not necessarily speaking in who's domain it is. More like who has more influence at any one time due to the seasons.
We have this quote from Summer Knight:
She beamed up at me. "Yes, dear. And this is Mother Winter." She gestured vaguely at the chair by the fire. "Don't be offended if she doesn't get up. It's the wrong season, you know. Hand me that broom."
This seems to indicate that the Mothers wax and wane with the seasons. I am extrapolating that their environment (the cottage) also subtly changes with waxing and waning of the Mothers. The cottage seems Summery in SK with the bread baking and Mother Summer doing some "spring cleaning."
In Cold Days this happens:
Mother Winter, in her black shawl and hood, bared her iron teeth in a snarl, though it was a silent one. She pointed one crooked, warty finger at the window nearest her, and blackened it with soot again. Then she shuffled over to a chair beneath the window, and settled into the resulting shadow as if it were a comforting blanket. "I do what must be done."
Mother Winter was able to alter the conditions of the cabin to better suit her. The Mother's power changes with the passing of the seasons and I think the cabin reflects that.
