What I found with my IF custom Ti CJ is that no bike is forever. In that I mean my fit and riding style has changed over the years. The bike is the same, I'm not. So while custom sounds great in theory, in practice it's just another frame that you will probably replace over time. That might not be true for you but that has been my experience. That's why the IF is up for sale. It's a piece of art but if it doesn't get used why keep it.
I'm sure though you will love your new bike. IF makes great frames that have a magic carpet type of ride quality.