I personally did not find parasite cleansing to be two steps forward and one step back. I got rid of them in 3 months and then went on maintenance and haven't seen any in about 2 years. If someone is having a much longer time expelling them I would guess that they are either being reinfected or not doing maintenance.
There really is no data that I know of to show that stones are the result of parasites. Maybe so, maybe no. Maybe they are due to diet as many people have noticed problems with gall bladder pain after eating greasy foods.
Everyone does need to do parasite cleansing, however.
Iodine is a very good thing to take though as the bromide that is put on produce depletes it in our bodies.