I don't think this is something to criticise really. For life really does mean as long as they can do it and have an interest in doing it. Sometimes it's really hard to let go, even if you're not involved with the project as much as you'd like to. I'm impressed when people can make that kind of decision before the lack of leadership/interest causes some issues.

Same reaction as to the pope stepping down - it's much better for the community if you don't keep a position where you can't do much work.