This is eerily similar to my own story, except that I'm 59 and still alive, so far.
I didn't work on drivers; I worked on mostly higher-level stuff (Newton, HyperCard, Quicktime, AppleScript, and several projects that did not ultimately become products). I worked at Apple from 1988 to 1998, and after that moved on to a successful startup.
In 2004 for I developed an incurable chronic illness. It was one that is hard to diagnose and hard to treat. I eventually found a doctor who could figure out how to handle it, and became able to work again.
Before the illness, I was in that category where I never applied for jobs, because there was always someone bugging me to go to work for them. In fact, my work at Apple was in two chunks because someone bugged me to go to NeXT, then someone bugged me to join a startup, then someone bugged me to go back to Apple. After Apple laid me off in 1998, two startups immediately bugged me to go to work for them and I chose the one that looked better.
After the illness, it has never been like that again. Since 2004, I have mostly been self employed, mainly as a contractor writing code and technical documentation. I choose to live in a place with very low cost of living, so that when I'm working I can stack up piles of cash to live on between gigs. I'm using one of those piles now to work on a product of my own design.
I've contemplated suicide a few times in what I think is a relatively dispassionate way. It was always during fallow periods when my buffer was getting threadbare, and I was in danger of becoming a financial burden to loved ones. I always decided against it because, first, it's irreversible and other choices aren't; and second, because the harm I would do to my loved ones by making that choice probably outweighed the harm I would do by becoming an expense to them.
Although I didn't make your friend's decision, I also don't judge it. I believe I understand in general how it can seem like a reasonable choice in some circumstances.
Since we're talking about ageism, I'll mention that I can't prove that the drastic change in my employability is a case of ageism, nor a case of discrimination against people with chronic illnesses. I suspect it of being both, though, partly because age and health are (not necessarily reliable) proxies for other qualities that employers are legitimately interested in, so I can see what the motivation might be, and partly because the differences between before my illness and since are just so stark and sudden.