"Asexuality is a description, not a commitment. If it changes in the future for me, then that's that. Either I was wrong about my orientation, or my orientation changed. It is thought that asexuality, like other sexual orientations, can sometimes change, but it is rare, and not by conscious choice. Basically, I'm not going to count on it."
Check out Skeptic's Play post, "Yes I Am Asexual"