Ummm...I can remember no less than 5 kids with a campfire, sleeping on a fallen log years ago
Much like a Bonzai...limit the root space and you limit the plant size.
I have an older one (8-10yrs) about that size, it is about 28" tall atm, but looks much more mature with bark on the "tree's" and moss all over the burl.
Quite frankly Mass...it was the only plant I could think of to get for your B-Day that you didn't already have! I hope Y'all enjoy it.