Once people decide to use gear they tend to go heavy constantly and never give there central nervous system a break. While your muscles may be ready for another beating your nervous system still could need a day or two off. You can still achieve amazing gains if not better gains by going light and chasing the pump, see how much pain you can really endure and get an amazing mind/muscle connection. Many very successful bodybuilders out there also believe this philosophy (Kai Greene / Rich Piana to name a couple of well known athletes that have achieved great success based on their bodybuilding lifestyle)..

Dont get me wrong you still have to go damn heavy to get that thick dense look and muscles that pop, but its those light days and them high rep painful sets that give you those striations and grainy look that completes the total package. What I have my clients do is stagger their heavy training sessions to allow for CNS recovery and to activate all of the muscle fibers both fast/slow twitch. Here is a small example just to demonstrate.

WEEK 1
Mon. Heavy chest day (barbells, dumbbells and weighted dips)
Tue. Light back day (Machine rows, seated rows, lat pulldowns, body weight pullups and chin ups)
Wed. Heavy Shoulders (barbell / dumbbell presses, upright rows, face pulls)
Thur. Off
Fri. Biceps and triceps (chase the pump for arms, I like drop sets a lot to really stress them out, you use your arms all the time and they really need to be shocked to grow though they get worked with all your heavy compound movements so no real need to risk tearing a tendon or getting bursitis in your elbows going heavy all the time)
Sat. Heavy leg day (squats, angled leg presses, stiff leg deadlifts, donkey calfs)
Sun. Off

WEEK 2
Mon. Light chest (high, medium and low cable crossovers, fly's and body weight dips)
Tue. Heavy back (deadlifts, barbell rows, dumbbell rows, weighted pull ups and chins)
Wed. Light shoulders (Drop Set dumbbell presses, side lateral raise, front raise, chest supported rear delt raise)
Thur. Off
Fri. Biceps and triceps (same as before but chose different exercises, 4 Movements for biceps and 5 movements for triceps 10-15 rep range, 4 sets per movement)
Sat. Light leg day (smith machine squats, lunges, inner/outer thigh, leg curls / extensions supersets seated calfs)

** Abs and calves and done alternating every other day**

That was just an example on how you can go light and still get amazing results while reducing the risk of injuries. After all, no one like to get hurt mid cycle!
You can also do DTP style workout on your light days which are very effective and will test your fortitude in every way. Here is a link describing that style of workout if you are not too familiar with it.
http://www.bodybuilding.com/fun/kris-gethin-dtp-4-weeks-to-maximum-muscl...

I never really have "off" days. Those are the days I work my rotator cuff, do some cardio, foam rolling or stretching.

Experiment with your own styles based on individual weaknesses and goals, just remember that its not the weight on the bar that matters but the quality of the contraction you are feeling when working each muscle group.