What I had in mind was something like people accessing raiding would be about 20% and LFR might add another 20-25% on top of that. I agree that most people don't run it a lot and it's pretty clear that many don't wait around for all of the wings to release once a new raid is out. Myself, I do it once to see it and rarely visit it again unless there's some 'fight' (to use the word loosely with LFR) that's more interesting than usual. More often than not it's a frustrating experience once you're in so it wouldn't surprise me to find that most only run it once or twice.