Since fall '09, so for over 5 years. I've been in the business for about 6 years. My earliest clients were agency clients - he's the only one I still see.
I have a few others I've seen since I was newly independent, which was in spring 2010.
These are people I deeply like and trust. They have become more than clients.
It's kind of a funny story about my oldest client. I didn't always appreciate him, to say the least. The first time he saw me, the agency got the time of our appointment wrong. They told me 7PM, so I was at the incall at 7. I waited a half hour, then 45 minutes, then told the booker I was going home. 10 minutes later, she called me, asking me to go back. I was like, 'That a**hole is almost an hour late!!' I couldn't believe she was asking me to go back and see him. But, she begged, and so I did. It turned out, that she had gotten the time wrong. He had scheduled for 8PM, and was actually right on time. But she didn't tell me that, and so I began our relationship with an unjustified grudge. A few dates later, we got it all sorted out, and 5+ years later, we're still seeing each other