Hello, I'm Completing My Health Care Advanced Directive, Determining Whether

Hello,
I'm completing my health care advanced directive, determining whether to direct:
1) artificial hydration be withheld, 2) both hydration and nutrition, or 3) just nutrition be withheld if a diagnosis of terminal, permanent unconscious condition.
Wondering how long one might live with hydration only. Is there more suffering associated with one of these choices?
Thank you.
Paula
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