I've been told the tank may siphon empty, and if I don't shut off the electricity the heating elements will burn out? True, or not to worry? Thanks!

Won't happen. Once water pressure equalizes it won't flow. I have a cabin in the GA mtns. always turn water off but leave electricity on timed for 2 hr. Per day. Been that way for 11 years.

Danno,
I always recommend turning off the power when there is the potential for de pressurizing the water heater and the connected piping. Siphoning can occur via the water heater dip tube, especially if there are cold water faucets or drain cocks below the level of the cold water inlet to the heater.
Idle, depressurized, energized water heaters, can also produce a rotten egg odor; this is not a frequent occurrence, but it is possible depending upon water quality, and the action of the water heaters anode rod. A complete explanation of this, and some valuable water heater maintenance information can be found at " waterheaterrescue.com "...