If your doing the 5 3 1, here's what the programs author had to say
From Blood and Chalk 11:
T NATION: Hey Jim, I'm a bodybuilder at heart. When should accessories be taken to failure?
JW: This is easy to answer. If the assistance lift is a multi-joint assistance lift and requires mental preparation, technique, balance, coordination (front squat, good morning, safety bar squat, Romanian deadlift, etc.) it's best that it not be done to failure. The risk-reward ratio isn't good.
Now if the lift is "easy" (face pulls, rear laterals, triceps pushdowns, curls, shrugs), then have at it. You can take most of these lifts to failure, get a good pump, and have no negative consequences to your training. These are the lifts you can mess around with, do some higher reps, and do what many people call "bulletproofing" the body ? flush blood into muscles and allow for hypertrophy without the strain of bigger weights and movements on the joints.
Think about it this way: train the big lifts "smart" and the easy lifts "hard."