Work becomes work when you no longer enjoy doing it. I worked until 69. I would go in at 8 AM and usually leave around 7 PM. I would seldom take a coffee break, just grab a cup and head back to my desk. Oftentimes, I wouldn't think about lunch until 3 PM although in the latter years, my stomach would tell me to grab something and I found it a good way to connect socially with colleagues or sometimes friends outside the company. If I had to do lunch on my own, it would be a fifteen minute break at a fast food joint.
After I retired, I missed the mental challenges. I retired when I did largely because combined demands on my time were becoming overwhelming to the extent that I would begrudge giving up any free time. Eight years into retirement, I still am loathe to set a schedule defining my plans for the week. I could have retired when we sold our startup company but elected to work for two more years for the company that purchased us to assist them in bringing out product to market.
The year after retirement we took a four week trip to the UK, Italy, and Amsterdam where most of our days were spent walking. Up to six hours a day. Today, back problems wouldn't allow me to do that kind of walking. In fact, I am loathe to even make an international flight.
My best friend, a year older than me, had a very successful insurance agency. I had been after him for years to retire and enjoy life. Last winter he sold his agency and I figured that he could finally get out and do some dishing and other things that he didn't have time for before. He still goes into the office every day, gratis, to "assist" the new agent in getting him on a successful track.