I think I like the term graduated, though I probably would not use it apart from this board.
Due to my circumstances, retirement felt a bit like giving up or surrendering. So I am working on trying to see it in more positive terms.
I remember an old movie once that had a teenage character everyone assumed was a drop out. People looked down on him based on this assumption. At the end of the film, you find out he graduated at 16.
I feel like there is a tendency to treat people who retire early as dropouts from the workplace. I feel saying we graduated from work early is more fitting.