My dad was diagnosed with a very rare type of stomach cancer called GIST at 42. The average survivability at that stage for GIST at that time was 6-12 months. Zero patients lived more than 5 years.
He was given experimental(at the time) drug called Glivec as it was being tested specifically against GIST and it was literally one of these "there's nothing else, so might as well".
He lived another 8 years after that, until cancer came back and the drugs stopped working.
When he was first diagnosed I was a teenager, my sister was a child - thanks to this drug he was able to see his kids go into adulthood, and obviously spend 8 more years with his wife.
How is that "ain't much"??????
Whether four or eight years, either is an enormous gift when facing a terminal illness. There is no question about it. It's even more so the case if a person is 40 years old than if they're 80. The 80 year old has already lived a full life, death is far more acceptable, tolerable, at that age for most people.
I suspect a person would have had to have never seen a loved one confront a terminal illness, to believe a year of additional time isn't a lot given the context.
My mother died relatively young from small cell lung cancer. At the time there were no specific therapies for it, it was often caught late, and typically a person would die within 6-12 months. Almost nobody would make it more than three years. She lived for around 20 months post diagnosis, and that was a lot of very valuable time, even if it wasn't enough time.
I've observed across my lifetime that some people live more in a year than other people manage to in a decade.
How quickly time passes objectively and how we experience time are obviously two different things. Perhaps the skeptical parent was failing to grasp the significance of the difference. When facing a terminal illness, how you experience time is drastically altered, even if the seconds tick by as they did before.