Although I'm far from experienced, still working things out, something I've read that rang true and did seem to help me when high doses of IF1 weren't:
When increasing water intake to very high quantities, drinking lots of water, put a little Sea Salt in the water; not enough to cause a flush (if trying to avoid an unexercised liquid movement that doesn't accomplish the goal of exercising the colon). More on this might be in the curezone Salt forum. It isn't mentioned often in the bowel cleansing forums, other than in concentrated salt water flushes, but doing small quantity Sea Salt in the high levels of water some people attempt for constipation relief makes a difference; the little bit of salt added does something plain water doesn't. I'm not explaining this very well, but maybe it is a seed of an idea.
Also, I think that for some people, stopping the laxative herb combination (and I'm calling IF1 a laxative herb combination) for 5 days then suddenly starting it again may cause a shift in effectiveness for the better. This happened to me, to some degree.