I know what I am about to say may not be the popular view here, but....
My mother died last year at 83. Four years before that she was not sick yet but named me in her living will as the person to make decisions for her in the event of her being unable to. She did NOT want to be DNR status, and made it clear to me that she wanted all possible chances pursued. This was not my preference but I was following her instructions.
Then she had a major heart/lung crisis. She was put on a ventilator and resusitated and many other things done. She seems likely to die, but she pulled through. After 4 months(!) in the hospital and rehab, I moved her to a nursing home near me. She continued to improve, and a year later she and I were able to have an entire year together where I could take her to restaurants in a wheelchair, we could tell stories and laugh and listen to music together, sit and read out loud under the trees in the courtyard. Yes she was forgetful and sometimes not happy, but that year was a precious gift we never would have had together if she had been DNR.

Later on she had more crisis, a stroke, and deteriorated again. In the end she was permanently on a ventilator and her quality of life was no longer good- she was not super aware anymore.
At that point I was told that I could supercede her DNR orders at any time, since she legally designated me to make her medical decisions. I still waited, and I rescinded her DNA orders only when her kidneys began to fail and she would need dialysis to survive in addition to the ventilator. We did not request the dialysis because we felt it would be too disturbing and unpleasant for her...and she was peacefully gone within 10 days of that, with me by her side.

I guess my point is that one can be on a ventilator longterm and still have some decent quality of life, even recover to an extent that one could enjoy good times with loving family for a while again. Being on a ventilator is not necessarily a permenant thing- vents can get you through a crisis- my mother went on and off one several times during her last 4 years. Plus, if someone is on a ventilator they can still request that their heart not be restarted if it ceases to beat. One can even feed oneself and talk while on a portable vent, which was amazing to me.
Of course there are degrees of all these things and nothing is ever as simple as we think when we head into it. I learned an awful lot that surprised me during my mothers' last 4 years and while I spent time observing others in that nursing home.
I was glad I got that extra time with her- it was difficult, but it helped me as well as her deal with her passage into her next journey.

I do agree that it is imperative to talk with the ailing person AND to get a living will and perhaps Power of Attorney drawn up legally and signed.
I think it helps to tell them that you want to be sure you can enforce THEIR wishes for them when no longer can speak for themselves. That you will speak FOR them and carry out their wishes. Tell them the "state" will make decisions for them if they don't designate you to. True, and scary!