Personnally, I mastered for close to 14 years prior to going on my own.
I was at Electrosound on staff doing remasters for tape of various artists, Bon Jovi, Janet Jackson, Nazareth, Steve Miller band, etc That led to a decade at Disney overseeing and mastering many many projects. I was so lucky to have worked with Bernie, Eddie and many many more. I opened Moonlight when I was at Disney and mastered projects at night. Stayed at Disney for almost 2 years for a structured paycheck, and then had enough clients to earn a living with out the big ears attached (not mine of course
).
So that's how long it was for me, and now we're in our 8th year of operation.
Nancy Matter
Moonlight Mastering