Yes, theoretically, conditioning can be broken, but it is extremely difficult. You described a situation that can happen, but how many people can actually organize their lives around that to face stuttering that way? And there’s a problem. The issue with "deconditioning" is that once conditioning has been established, it can resurface if we face aversive situations again. So, if you go through all the effort of deconditioning, weeks doing that exercise as you describred, and the following week someone makes a joke about your stuttering, this experience can make your progress regress, as you are conditioning again stutter + aversive condition. Of course this depends on "how aversive" is a stuttering joke for you. For exemple me, there were times that I'd be mortified listen to one, but nowdays I am ok. So the aversive property" of the stimulus also depends on our relation with that. Stuttering demands you to be tough :) And that’s pretty much what happens—people who stutter are constantly dealing with aversive stimuli, whether it’s being interrupted, a joke, someone ignoring them, and so on. All of this keeps the process in an endless loop, never fully resolving. Moreover, there’s something even worse: when we ourselves become aversive stimuli (and that might be the hardest part). When you stutter and immediately have a verbal response (thought) like "I will never be able to speak fluently" or "I am inferior to others," that thought itself can act as an aversive stimulus and slow down the deconditioning process. In other words, it’s necessary to work on multiple fronts at the same time to break free from this, and even then, it’s difficult. In the end, as you said, there will still be a neurological difference that means we will always have some fluency rates differences compared to people who do not stutter. But it will be smaller, as the emotional factor will be less intense, and so stuttering. That's the theory. But of course, in a very emotion situation (even not related to stuttering), like losing a relative, or being robbed, your emotion will be so high that your stuttering will be more frequent. And then you have two paths: to think, "Oh no, my stutter is back again," and suffer from the aversive properties of this verbal response (which is what most people who stutter do), reinforcing all your negative beliefs about yourself or stuttering, and turning yourself once again into a major aversive condition for yourself that will for sure amplify the conditioning; or to understand this process, stay calm, wait for it to pass, and remain firm in the belief that you can deal with stuttering.