The open field of shingles is the part that almost never fails. Water gets in at the interruptions: the chimney, the valleys, the pipe boots, the step flashing where a roof meets a wall, the eaves. Above that roof is an attic whose temperature and moisture decide how fast the deck ages, and below it are gutters that decide where every gallon goes. Treat those as separate trades and you get a new roof over an unventilated attic, draining into undersized gutters, failing early for reasons nobody connects. We handle them as one system.