I've had one since high school but I keep a cheap $15 a month second line. I've changed numbers on that line because I use it for everything spam related. Though I haven't changed it in about 2 years. So it might stick around a while.
Never. I had the same phone number since I got my first cell phone at the age of 12. I am 31 now. Same phone number. So...19 years. Also AT&T, through various weird Cingular smartphones, until the iPhone came out in 2007, and they say, the rest was history.