I've never worked any job for more than 5 years. I fully appreciate that I am in a market for labor, not a dating service for relationships. That said, I expect to be in my current job for many years.
My longest job was nine years and am about to match that with my current one. Most of my other jobs have lasted about two or three years.
I usually get bored pretty quickly woth jobs. Once the initial training is done and I get the hang of it I'm usually bored of it by then. If someone offered me a decent wage to leave mine and do something else I thought would be interesting I wouldn't hesitate to go try it out. There are a lot of interesting things to do out there and spending my entire life doing only one of them would make me feel like I cheated myself.