I too take it as needed.... and my surgeon told me that I needed to split the dose, with a half packet (I get mine in packets now, instead of the container) twice a day (once in the morning, once before dinner).
It does certainly help some sometimes... I can go without it but then I will have to expect more bowel movements. I am taking it again today with immediate response again due to some extended traveling I am doing tonight through tomorrow. Though I do believe sometimes it doesn't help... I know after my surgery that I had in 2007, it didn't really do anything so I stopped taking it. Though after this one that I had a month ago... it is making a difference.