Yes, Nathan, I also start out at EI 12, but the bracketing does cover 3 and 50. I could shoot Kodak just at straight 400 with no problems, but Konica, Efke, Ilford, and (I'm currently trying) Rollei, they don't have the same great response. Of course, I'm really glad just to have anything at all these days.
Also, when I'm out photographing in IR, I've done stuff at the break of dawn, in deep forest, and at the last fading rays. So yeah, the bracketing needs to cover all that. Such is life with IR. I do know that some people have modified their light meters, and have removed the IR filter. The problem is that what I'd need is a spot meter, because some of the conifers don't reflect any IR in the lower spectrums where the current crop of films is sensitive to it. I have a few shots where some trees reflect it modestly, and others don't reflect anything at all.