By the time the sidewalks along North Street are walkable again, most people never learn what hour it took to get them that way. Valor Enterprises Corporation handles the winter side of North Reading — plowing driveways and parking areas, clearing steps and walks, laying salt along the shaded stretches the sun never reaches. Storms here run long, and the second half is usually the harder one, when the piles are already high and the wind is still working. The satisfaction is plain and physical: pavement showing, edges square, a path wide enough for two people to pass. Then the truck rolls on to the next street and does it all again.