I think we all have different outlooks at best and unfortunately to often the one who is dying did not make clarification of their wishes before their time came to pass. This is no ones fault it's just something we don't like talking about and it shouldn't be, because whether it be a teenager or senior it's a part of life that should be acknowledged, along with ones wishes when the time comes.
I personally have a living will on record at each local hospital in case there is not any of my loved ones close by at the time. I also (with much criticism from friends) usually have a DNR due to other medical issues I do not wish to have treated. I do not want to spend the last of my days hooked up to machines as others torture themselves trying to make the impossible choices given to them without feeling doubt, second guessing themselves, or remorse for a lifetime.
I believe that is in an individual choice and one that should be made known as soon as they are old enough and able to understand the process, along with knowing all the facts. I mean as soon as they are capable even if they are teenagers!
I'm not talking about getting into some gruesome conversation about death,etc. Just letting them know your wishes and asking if similar circumstances were to occur with them (tragic accident, etc) what would they want.
All to often we make emotional choices trying to hold on to someone for ourselves. It's just part of being human,. The problem is the one who is dying is being tortured themselves knowing the turmoil others are going through with the choices that should have been made earlier. Believe me they may not be able to show it, but they know!!
Again, great question!!!!