I don't think that there is a real progression that is typical. I have done 7 flushes over several months and had flush number 3 and 4 be mediocre in stones, very little came out except bb sized ones and chaff. But I FELT like I had more and glad that I persisted and got out stones as large as a small walnut in flushes number 5 and 6. I still will continue to flush every 2-4 weeks until June of next year until I am "stone free" or nearly so.