Doable for certain. I'm not sure why you'd want to make it lower though, 4-5 lumens or so is a reasonably low power.
I did a runtime test on mine with another member of CPF, and we both got over 48 hours of usable light from an alkaline battery. Don't bother using a lithium in an Infinity--the way the electronics work it drastically lowers your runtime (runs brighter for a shorter period of time)