We've always turned ours off, and our trips are rarely longer than 2 weeks. The first time, I overlooked something that ended up costing me $400.
Our house is a 1700 square foot rambler, with the hot water heater in the west end of the garage and the kitchen at the east end of the house. The hot water pipe run is close to 90 feet. The builder included a hot water re-circulation system so we didn't run a gallon of water at the sink before it got hot.
I forgot to turn the pump off when we shut down the system. We were gone for 10 days and the pump was seized solid when we got back. If you have a re-circ system be sure to shut the pump off before turning off the water supply.
