By the middle of December it is dark in Mount Kisco before anyone gets home, and a driveway untouched since morning becomes a real problem at half past four. NY Landscape Lighting handles the winter side of a property — plowing, shoveling walks and steps, and putting down salt wherever the packed track has turned slick. Storms roll up the Hudson Valley and stall over these hills, dropping more than the forecast promised more often than not. There is a plain pleasure in clean black asphalt under headlights, the banks pushed back square, the walk passable in ordinary shoes. The area covered runs from Mount Kisco out to Bedford Hills, Chappaqua, Armonk and Pleasantville.