Some of the stones can be real old. Years. The bright green ones are the new ones. The older they are the darker they get. If in there long enough they turn gray or even black. You can tell when you're getting to the end by the color of the stones. Once you get to the old ones you know the livers coming along real well and isn't going to need much more work. Just stay on the bug killer for a year so no more stones develop. After you get to the point where no more stones are passing do a couple more flushes anyway at about one month intervals then if no stones back off to twice a year. Unless you feel the need, sometimes the lymphatic debris will clog you up. Play it by ear - do as needed.
It doesn't take long to make a stone, probably only a couple days. It protects the body from the parasite. But after a while the liver can't hold anymore and the secretions from the parasites get into the body anyway. That's when all the symptoms start and the cancers start developing.