I also ordered two extra #6 straws as back-ups to replace the ones with internal residue build-up. Matthew easily transitioned from the previous straw to this one as they were the same diameter. Like the previous straws, he used this straw for most of his drinks including chocolate almond milk, orange juice, apple juice, and water everyday. The straw was sent to his preschool as well for him to use at snack time.
I'm not sure if I had mentioned it in any of my previous TalkTools straw posts but Matthew is on straw therapy as recommended in his NACD program. So we also used the straw as part of a set of oral motor stimulating activities specified in his daily program.
Matthew started on straw #6 during the Christmas break. He could've moved on to straw #7 after a month but I kept him on this straw for almost 3 months because there was so much going on that I just kept forgetting to move him on to the next straw in the hierarchy. It didn't hurt to keep him on the straw longer anyway. The instructions only discouraged from moving on to the next straw within a few days, which would be too fast of a transition. As of April this year, he was on straw #7.