A Saturday morning in an Islip neighborhood has a sound to it, and mowers are most of that sound, from the first houses waking up until the heat pushes everyone indoors. RR Vargas Lawn Service inc. is part of it all season — cutting on a weekly rhythm, edging drives and walks, trimming whatever the mower misses, sweeping the clippings off the pavement before pulling out. The growing months here stretch from April clear into November, so the calendar is long and the routine is the craft itself. Cleanups at either end handle what the trees and the wind leave behind. The rest is the plain pleasure of a lawn that is always, reliably, just cut.