Bill, not sure I have any insight in this but I have my own stories.
My dad died of congestive heart failure about 14 years ago, he was in the hospital 2 or 3 times for short durinations during his last 6 months. But when the end came he was in the hospital for about a week progressively getting weaker until there was only enough energy in his body to breath and move blood, he was basically asleep for the last 2 or 3 days. It was hard, but I was fortunate that I talked with my dad every day for the last year or two of his life and we said everything there was to say.
Now in contrast, mom died of cancer, and it took her well over a year to die. She was actually in a hospital in Chicago when dad died in the local hospital in Indiana so we had to get her out of the Chicago hospital to take her to the funeral. Mom's death was very difficult for us as it dragged on for a long time. Dad, in comparison, went pretty quickly.
We just lost my uncle a month ago. He was in the hospital but doing very very well, joking with people, watching TV, etc. The doctors told us he would be released to go home the next day. Well that didn't happen as he took a turn for the worse that same evening. I got a call in the morning that he was not going to make it. He essentially died about 2:30pm that day, but was on a respirator that was keeping him breathing and had a pacemaker that kept his heart pumping at a minimal level. A decision was made to keep him on the machines until we could get his 2 grandsons to the hospital, they lived in the same town and were being picked up from the middle school to be brought to the hospital. So the official time of death was after 3pm. Personally I think his death was a shock to the family, but he was also an unhealthy person and I think people knew he could have died pretty much anytime, any day. It just happened that particular day.
My father in law died a few years ago. He went into the hospital on a Thursday with a back ache and his funeral was less than a week later. He died of lung cancer. Nobody had a clue he had it. He was healthy in every other way. It was a total shock to the family when he died. Nobody expected him to die.
My mother in law died a couple years ago. She suffered from advanced MS and had other complications. Her death was not a shock, she simply declined over 20 years. As ready as the family was for her death, there was really no getting ready for it. It seemed like everyone knew she was sick, and it was just part of her life, so nobody expected in on any given day. I think her death was still hard on her children despite her ill health and despite the fact that everyone knew was declining.