Thats what i would do, leav it on for a month, and then try turning it off when your not using it for a month. That would be the best test. Or you could get all technical and calculate how much it consumes by how many hours its on and then subtract the time you think you would turn it off and see if that makes a big diffrence on your total monthly usage?
And like the other two above me said. In a way your better to just leav it on all the time, Because when it gets turned off and on all the time the parts go thru a lot of temperature change which causes stuff to expand and contract and ends up causing more harm then just leaving it on all the time. well i cant think of the right words right now so ill leave it at that.