Ever just get tired?

i can still outwork most 85 year old men(and im 56)
Ya know that's not as odd as it sounds.
When I was a lot younger I heard it said that if you don't use it you lose it.
Well now at age 65 I am living it.
On Tuesdays, I police the local landfill, making sure the various types of garbage arriving there, go to their proper destination. On this day I might lift as much as 1000 pounds in summer to as little as zero in winter. This is repeated on Saturdays.
On Wednesdays I chuck garbage; between 4500 and 5000 pounds usually.
On Thursdays I chuck recycleables, about 1000 pounds worth.
Fridays, Sundays and Mondays are "MY time"
But from Thursday afternoon, to Tuesday night, truthfully, I do very little physical work.And on Wednesday morning I know it.
So my wife got a dog; a 66-pounder. Who needs to be exercised twice a day. For a total of over two hours. And guess who gets to run, walk, and bath, the friggen exercise machine; hyup me. But that seems to be enough to maintain.
Now 85 is twenty years into my future, and I recently told my foreman that this was the best job I have ever had and that I will never quit it. I guess we'll see. I'm expecting the end of the age long before then, and I guess we'll see about that too.