It's about more than a few dollars saved.
When I'm gone that long, I don't just turn off the water heater, I also turn off the main water supply.
A few years ago, one of my customers from California move here, bought a nice house on a three foot deep crawl space, moved in, and went on a cruise a few days later. Nobody in the neighborhood knew who she was or how to get a hold of her.
A few days later, one of the neighbors noticed water coming out of her crawl space vents. Knowing nothing else to do, he shut the water off at the meter.
Turns out the washing machine hose burst, flooded the whole first floor ruining the wood floors, seeped into the crawl space, eventually filling it up and pushing water out through the vents.
Cost her insurance company about $50,000 to repair the damage and make the place livable again. Not to mention the inconvenience of finding temporary living quarters while the damage was repaired.