My response:At what point in my life should I do an MBA?
The best way to get an answer to that question, is by replacing 'MBA' with 'Root canal'.
Get an MBA (or a root canal) only when you feel the real need for it. They are both expensive and painful, and the (financial) recovery phase can be long & equally painful.
Also, don't assume that you WILL need it.
For most industries and jobs (with exceptions like consulting or Investment banking), a basic relevant qualification (like engineering) topped up with quality experience is valued more than an MBA.
In fact, there are exceptions in those industries as well. You may have read the inspiring story on the MBA Crystal Ball blog about an IIT grad who dropped out of an MBA program and now works in a management consulting firm.
If you don't have a strong rationale for it yet (you'll need to articulate it in your MBA essays and defend it in the interviews), then don't jump in.
You'll always have the opportunity to take it up when you have the right understanding of where you want to take your career.
...and there are more than enough dentists who offer root canal services when you need it. Just don't sign up for it now assuming it'll help you 5 - 10 years later.