personally, i do a light week every 4th week. all of my workouts are full-body o-lift based and pretty cns intensive, not too mention i'm really active outside of the gym as well.
if i feel normal on the light week i cut back to half volume, sometimes even less, but i'll still go pretty heavy.. 80-85% ish max. but if i'm feeling drained, as you say you are, i don't go near max effort and still cut the volume in half.
some people think every fourth week is too often to go ez but it's what i need to do to keep it going for the long haul. the trap i have to watch out for is usually on the 2nd or 3rd day of the ez week i start feeling really awesome and so i go nuts and even hit a pr here and there, but i end up paying for it by being sluggish for the next week or even two...
so ,for what it's worth, that's me and what i do.