I did some research on GoldenRod dehumidifiers and found that it generates less heat and is more economic than a light bulb.  The surface holds a temperature of 150 degrees and inside a safe, the air temperature will be only a few degrees higher than the ambient temperature.

My question is: Is prolonged storage of ammunition recommended in a safe with GoldenRod?

Won't a Goldenrod dry up the oil coating the guns in a safe as well???????

A few degrees is all you want so moisture in the air won't condense on the metal.  This is how they work.  This wont hurt ammo.  Storing ammo in say a shed that gets 125 degrees in the summer and 20 degrees in the winter will deteriorate ammo.  I've had my goldenrod in my safe in the basement for 13 years without a hint of rust.  Some of my non-shooters get cleaned maybe once every 2 years.  I think its the way to go.