End of Life Issues

I watched my grandparents and father suffer (Grandpa with cancer, and Grandma with dementia and then pneumonia hooked up to a machine, and my father with cancer) and it brought the thoughts of end-of-life dying to a terror.
All three were slow.
My grandma was hooked up to that ventilator for over a week and she had tears in her eyes and made pitiful sounds the whole time. Many in the family couldn't stand to see her like that and stopped sitting with her--instead waiting at home for the final call. All three were in their eighties at the time of their deaths. My grandfather and then my father (years later) suffered the slow progression of cancer that took over their bodies and lives. There was no joy--just pain and the loss of any ability to attend one's own needs and functions. Their bodies wasted away until they were half their sizes.
There was no chance of a turn around for any of them.
We would not allow our pets to suffer this way.