I have a 16 year old State Industries 40 gal propane water heater. It currently works fine (only issue I've ever had was to replace the thermocouple a couple of years ago). However, I'll be away for two months, and I worry what would happen if the water heater gave out and began to leak while I was away. Rather than have the possibility of water running non-stop and flooding my house in that scenario, I want to shut the cold water inlet valve off going into the top of the tank. That way, the worst that could happen is that the water in the tank would drain out if it leaked (which really wouldn't be that much of a problem). Unless it's absolutely necessary, I really don't want to drain the tank, turn off the pilot and/or turn off the gas. If it's not unsafe or going to damage the water heater, I'd rather just turn the cold water valve off, and when I return to the house, turn it back on and wait for the water to heat up before using it again? Will that work?
If you turn off the water supply to a hot water tank, you should also turn off the heat so that there isn't a chance of heating an empty tank. Leaving the pilot on is fine, but leave it set to pilot only.
Other than that, it's a fairly standard practice to shutoff all the water, not just the hot water, in an unoccupied vacation home. I would recommend a 1/4 turn ball valve, instead of the traditional gate valves, because the latter are prone to failure when used. It's also important to set the thermostats in the home to keep it warm enough to prevent any pipes from freezing inside the walls if your location gets that cold.