You might consider buzzing with no guard, you're so close anyway. The haircut will last longer. It won't be bald, but will give you a good idea of what it will look like. But won't feel the same.
When you do shave your head, you'll be another guy who says I wonder why I waited so long.
Buzzing no guard results in a very interesting, tight feel on your head. I first buzzed no guard on a vacation to Maine. Part of what moved me to sly a few months later.
