I can't see how they can be any less effective if you split them up, but I can see how taking them all at once could be less effective. Everything else being equal, you are taking the same number of pills a day. Spliting them up just guarentees that any benefits to spliting them up (if there are any) will be realized.
We take this stuff to grow. I am sure the pump or rush that the once-a-dayers feel just before a workout is not due to a sudden growth spurt. That is BP or water or some other effect.