Usually after I've rinsed the sponge, it's back to clean and OK to move on with around the car.
I copied one of the guides set up on DW for the ONR wash methods.. Damon, the chap involved, put a few horizontal and vertical slits in the sponge to create 'channels'.. Whether or not it helps me or not, I do not know - I guess the idea is to give the dirt somewhere to go (away from the surface)
Mind, after I've cleaned said area with the slitted side, I switch it over usually and give a few more passes on the solid edge, so... *shrugs*