L.W.
I have two boys and the older one sat for about a year and the younger one always stood. I recommend having him sit for as long as possible. The mess when they stand is unbearable, they miss, shoot the tub, it gets everywhere! Also, if you put a drop of yellow food coloring in first and then they shoot at it and watch it change colors (which they can't do sitting) that can be a good incentive if you really want him to stand. Good luck.