I don't think you have any serious blockage in your duct. I guess you would not be able to digest foods at all and the pain would be unbearable. There is a very little chance that such thing happens after flush.
You will feel very well after the flush, that is how you know that everything went well. If you don't feel much better, flush again after sometime untill you finally do.
As for stone free condition, you are right, it is not permanent. Stones will still keep forming untill your body gets rid of all the gunk it stored during all your life. It may take years.
But it is very important first to flush every two weeks untill your first stone free flush (when you get no stones out), even though you would feel totally great in between the flushes. This is to make sure you clean your liver from all old stuff.(My 5th flush was stone free). After that you can just flush for maintenance, or whenever you feel like. (I flush every two-three month when I feel some discomfort in my liver area).
There are a few people here who finally got to the point when they don't get any stones after such maintenence clenses. Southern Belle, for example.