An extremely rare case of sexual fluidity in males: The Day I decided to Stop Being Gay.
This anecdote is similar to the qualitative study by Lisa Diamond, published in the book Sexual Fluidity, who documented 100 lesbian/bisexual/other women who spontaneously changed sexual orientation over the course of the 10 years after they graduated college.
The theory of sexual orientation that I'm familiar with are that female sexuality is more fluid, and male sexuality is more fixed --- though neither sexuality can be made to change, but rather may change spontaneously --- but this anecdote is an example counter to the view of male sexuality as being relatively more fixed.
He says he has another friend with a similar story. Will people start speaking of "gay until straight-marriage" as they do "lesbian until graduation"? GUS (GUM?) is a better acronym than LUG anyhow.
I wonder how it will turn out for him in 10 or 20 years. I do think that any woman would justifiably hesitate to marry him.