Weeks at the minimum. It takes 21 days to make a habit, and 90 days for the brain to change its neural pathways. By practising, my speeech becomes smoother. There are relapses. Right now I'm going through a bad relapse :( Its been many months taking therapy, and I need a session almost every week to keep up with the flow of speech. I do feel like there is massive improvment on days I am not effected by outside elements-Stress, tiredness, sleepnessness, thirst etc. And yes, I do sometimes stutter when affected by outside elememts (Mentioned in the line above).