Only a couple of years. I first heard about them a little before The Witcher 2 came out, but my PC wasn't capable of running it so I didn't get to play it until it was released on 360. I loved it so much that I bought the PC version and the original Witcher for the day I finally got a GPU. Now I have a GTX 670 and am playing the games the way they're meant to be played, excuse the unintentional nvidia pun.
But yeah, I've been following them since I'd heard of TW2, despite not actually playing any of their games for about a year after that.