We're all going to die at some point, and while most/many of us might want to delay that inevitability as much as possible, I don't think it's warranted at all to assume that the same premise applies to every single one of us. This guy realized that the only thing in life he could truly enjoy was climbing rocks. Do we really need to fault him for deciding to then just do that thing until fate eventually catches up as it always does?
Sure, it may be rough on the people whose lives they intersect with, but provided they're not a parent raising a child/children/etc, acceptance of one another for who we are is all that remains. Personally, I'd take short-lived good company over long-lived mediocre company any day.