> I am in the early stages (just a few months in) and I am hoping to work towards this level.

Congrats!

> How long did it take for you to go from a few stable clients to too much work to handle?

About 4 years. It's definitely a long game. The first years were pretty rough. Although, to be fair, I started doing work right in the middle of a recession.

Good luck! Also, I'm happy to answer any other questions you might have. Feel free to contact me directly, too (email in profile).