I had a single lever, clothes washer shut-off valve, replaced after it began leaking. It was eleven years old. During this period my wife had always turned it on before washing and off after she was finished, approximately 2-3 times per week. The plumber advised me that it was better to always leave this valve on and only turn it off, when out of my residence on extended occasions. He said this would prevent wear and tear on the valve and it would most likely last longer. This makes no sense to me as I always believed it best to turn off the valve, when not in use, to avoid a disastrous leak. I'd appreciate any opinions on this. Thank you.