At times when I have abused this perk to it's fullest extent, setting up finishers and elemental melees to where I can keep a momentum of things, I noticed it has a hard time computing time and time and time and time again. This may be brought on by sudden changes in weapon or armor loadouts, as I seem to change them frequently as well, but never take off the helmet. It eventually returns, albeit unknown triggers, sometimes with a change of scenery, (passing through a load point) but not always.