When working to learn, what lessons should you seek and when do you know it's time to move on?

A quick background about my situation. I’ve always run my own business until last year. I’ve had some business success in the past having sold my first business at 24. I have produced millions in revenue and am doing my own property development project. I’ve also had my fair share of failures. I’m 26 now.. I have a broad range of skills in business, marketing, property development and design. I now work for a big time property developer who has billions of dollars worth of projects per year.. My questions are; – do you think it is worth working for someone to learn? If so for how long? I was originally under the CEO who has 250+ staff, now he is busy so it’s hard to learn from him other than when I’m in meetings and he is present. – Is it best to just go out and run your own businesses? – What would you do? What would you look for? – is there anything wrong with having your fingers dipped in many pies or is it best to laser focus on one specific business or industry There is definitely a correlation of learning then earning so would love any advice or tips on this. Not sure who else to ask. Thanks for your time, I really do appreciate it. Tas