It is unwise to rush to have a living will done by practitioners from the same branch of government that has exercised this power to kill. I also worry that the wording might end up tied to funding or lack thereof in law for disability care, or, that if a person doesn't have one in future somehow, the physicians will just kill you by default. Interpretation of the wording now of such instruments will open its own vigorous law practice, and permit doctors to end the lives of people who might otherwise recover but for these documents. Finally, I do not want a euthanasia advocate dressed in sheep's clothing to hand me my hemlock-laced death warrant. I keep hearing the line from the old WWII movies, "Do you have your papers?"
I strongly disagree. I am a lawyer and no matter which side of this issue you are on, you should write down your instructions in legal form. This case proves it.
Think of how much bandwidth has been devoted to whether or not Judge Greer (and the appellate and reviewing courts) accurately or fairly determined Terri's wishes. If you don't write down you wishes, you risk the same type of dispute for your heirs.
So whether you want to maintained on life support or withdrawn from life support, write it down in enforceable form. [Most states have forms you can fill in yourself and state your wishes.]