I'm with Hywel on this one. I just started fly fishing and tying a couple of months ago, and I can't stop. I usually tie a couple of them as soon as I get home from work, and then my wife and I eat dinner, and I'll start tying again for a couple of hours.
I've even had moments where I couldn't decide whether or not I wanted to fish, or tie.
Maybe it that I'm so new at it, and maybe it's that I'm so glad to be out of college and have time for things like this. I really love it: there's something that feels really good to me about having learned something all on my own.