20-35: Find and build your skills/industries/networks and start to align that into a career. Don't be afraid to make mistakes to enhance learning.
35-50: Double down on the skills you have in the industry you know, build your personal brand, achieve your career goals.
50-65++: Give back to those earlier in their career, pay it forward, pass the torch etc.
With that framing in mind, mid career would be at least 15 years. I think what is interesting is most people underestimate how long their career is.
ps - I think the above notion is loosely based on a book I probably didn't read completely []
[] https://www.slideshare.net/BrianFetherstonhaugh/the-long-vie...