There’s not one specific age you’re going to find is The Answer to this.
When you are young and still developing and have lots of time to find your path, it’s worth making the long term investment of some general schooling to maximize your own growth and development, and prepare yourself for a broad set of possible futures.
However, as your career progresses, it becomes less valuable to invest in general schooling, but specific training for your specific career can still be valuable.
There’s no cutoff point where all this flips. If you are 5 years into your career and still aren’t certain of what you want to do, an MBA may still be valuable. It will expose you to a range of skills and possible roles and give you some good general foundation for things like leadership roles, or starting your own business.
If you are 20 years into your career and want to rank up to earn more money, an MBA is probably more expensive than it is worth. At that point, your experience is much more valuable than shy degree. Sure, you might look better in a job interview with MBA on your resume, but getting an MBA is expensive and whatever small advantage it gives your resume will probably not pay for the cost of the MBA.
You need to figure out where you are in this journey. Do you still feel that you are exploring and looking for your niche? Schooling might help. Are you on a specific path and hoping to power up? Schooling may not help.
I am 20 years in. I took a class for $300 last year that was highly specific to my role and only required two days. That was worth it. Spending $40k on an MBA will not be worth it for me. I could be 38 or 54 years old, age isn’t really the point.
Did she do it for the joy of learning? Or personal growth and satisfaction? Or was it for career enhancement?