From what I have read, the abs are more of endurance type of muscle, and can handle alot of stress. However, I believe the best approach is to allow rest inbetween WO sessions to allow muscle recovery/recuperation/rebuilding.
Some will tell you to allow rest like you would any other body part, some will tell you differently. See how YOUR body responds to this stimulous, if after a few weeks (OF PROGRESSIVE OVERLOAD WITH THE ABS) of what your trying to do works, then fine. If not, you need to re-evaluate your training and rest ratios.