Eh, the old coots I met weren't dopers and definitely had all their marbles. Some had wear and tear from doing 20+ years, but mostly all of em were sharp as a tack.
Know what type of guys were the most unstable? Middle aged white collar guys. They were some pill-poppin, psych med heads. Ever see pics of chin when he was bathrobed up, giant oversized wool hat, slippers, the whole bit? That's what these guys looked like.