I wrote a while back in a speculative post on the nature of human sexuality. I used the metaphor of language. You could always learn to speak other languages but your first would always be latent. This metaphor matched what I witnessed growing up. Two different friends were straight, bi-sexual, then became exclusively gay. It was a slow process spanning about eight years each. When I wrote that post I had no idea that research had been done.
The University of North Carolina’s National Longitudinal Study of Adolescent Health surveyed 10,000 teenagers and found that the vast majority of sixteen-year olds who reported only same-sex sexual attractions reported only opposite-sex sexual attractions one year later.*
It is not surprising. I think that over time one’s sexual identity becomes tightly intertwined with their self-image and becomes difficult to alter — difficult but not impossible if one so desires.