That's very sad to hear. I'm far from active here, these days, but I've been at the periphery of things for a long time, and you get used to folk being "part of the furniture". Sorry to see him leave us.
Getting older is... complicated. I'm active in the local dementia community and there is definitely such a thing as living too long. But there's also such a thing as not living long enough. There are no rules when it comes to fairness at either end of that range.
RIP Rob.