Yaker, I have to agree with your Dad. Hard work won't kill you. I used to work 100+ hour weeks for 6-8 weeks straight and then maybe a couple of weeks back to 80 or so and it made me better for it. I like to think that is why I am in as good of shape as I am. I farmed and once I got the crop out, I would hunt almost as hard as worked.
I have slowed down since 50 but I still have to stay busy.