I left my corporate career at 36, because I felt I had done everything there was for me to do in that company - I had enjoyed working there, and done very nicely.
I became self employed, during management consultancy, change management, and management training, mostly for big businesses, but also for smaller ones.
After 3 years I had an opportunity to buy half shares in a technology company, so I did. I still have that half share. I also bought shares in a small number of retail businesses - most of those I have subsequently sold.
I am now 56. No one employs someone who is 56. So I shall continue to work in the business I partly own.