A Ti bike is probably 'forever' - but I'm not sure that matters all that much to some of us who would like to have something new every 4-5 years anyway. Or perhaps it gets to the point where the more you ride (and I ride lots of miles) the more you need at least two good road bikes - and at that point a 'forever' bike is a good thing to have in the garage. My Ibis Titanium is my permanent 'second' bike now - after being refinished and refitted - I'm hoping that 1995 model is still under my ass when I'm 70 years old (I turn 50 next year and I've been riding the bike for 10+ years already).
I have to honestly say that if I was forced to choose one bicycle forever, I'd either keep the Ibis or go out and buy a Serotta or Seven cycles Ti model and forget about buying bike schwag. Like that's ever going to happen being on THIS stupid forum. Right.