Long or short idle animation?

I'm creating some animations on Blender and for some reason (please disregard the why) I have to create an idle animation which will make my Tank basically do NOTHING, just stand still.

My question is simple. Should I create a one frame only animation which will be in loop and since it's one frame it will be looped very fast or should I create a longer one, let's say, 250 frames which will also be looped and since it's longer, be called less times?

Thanks in advance!