The further apart the trees are, the higher the attachment points need to be.
Your hammock will be hung so its comfortable to get in and out of. Typically around chair height. This is the constant in this equation.
If my trees are close (say ten to twelve feet apart), I will attach my webbing around five or six feet off the ground. As the distance increases, my webbing must go higher to maintain the 30* angle. The trees in my backyard are 20+ feet apart and that involves getting my straps high (8 feet approx.) to allow for a good angle. I used a ladder to install the straps, but this is at home and was easy to do.
Site selection is the woods is usually easy, I know the distance is good when the trees are twelve to fifteen feet apart. That gives me room for the tarp and easy attachment height for the hammock.
The 30* suspension angle theory is only a recommendation. If what your doing works for you and you find it comfortable, then continuing doing so. hyoh.