I'm pretty much with Countryboy on this. Even if they are on 40 acres, how much control do you have over who approaches the bees? I, and probably you, do live in Africanized territory and I have bees that become Africanized. The thought of some kind of power equipment, or truck, or who knows what, disturbing an Africanized colony might keep me awake at night. Of course, I don't know the exact situation, but what is the risk/benefit ratio? Is the location good enough to warrant that kind of risk? Beekeepers in Texas have been successfully sued for attacks that have occurred when a third party used power equipment in the vicinity of the bees.
Private landowners, where I keep bees, know full well that they are to keep away from my bees, and they leave any brush maintenance up to me.