Mine came after 16 months. My teacher didn't let me to practise sight reading at all, even I asked him on this topic a couple of times. It turned out that I made significant progress after he started me on Bach 2 parts invention a couple of months ago. Before I was on Sonatina, I could easily remember the melody and the companion usually comes in patterns. But with 2 parts, the music is so unconventional (unconventional comparing to classical and contemporary music) I have to read the notes one by one every time I play. I only realized this progress after my teacher gave me another piece on Sonatina.