I just placed an order for my first L series IS lens, the 70-200 F2.8L IS. Very exciting, I can't wait for it to arrive, but I have yet another question. Do the IS lenses suck substantially more battery power from the body? Any idea how much momre rapidly I will wear out the batteries? Or is the IS a lower power draw than I am anticipating? I'd been considering a battery grip for my camera (300D) anyway, partially to help balance the weight of the lens and also to give me more life. But I am wondering as I start using this new lens extensively (which I imagine I will, since it is by far the best lens I will have) will I NEED to have the extra batttery life?