How about a 2006 study (abstract below)which shows the fluidity of sexuality from youth into adulthood. Only 57 percent of gays and lesbians did not change. While most do remain the same identity there are still millions who don't. Hardly rare by any stretch.
A longitudinal report of 156 gay, lesbian, and bisexual youths examined changes in sexual identity over time. Fifty-seven percent of the youths remained consistently self-identified as gay/lesbian, 18% transited from bisexual to gay/lesbian, and 15% consistently identified as bisexual over time. Although youths who consistently identified as gay/lesbian did not differ from other youths on time since experiencing sexual developmental milestones, they reported current sexual orientation and sexual behaviors that were more same-sex centered and they scored higher on aspects of the identity integration process (e.g., more certain, comfortable, and accepting of their same-sex sexuality, more involved in gay-related social activities, more possessing of positive attitudes toward homosexuality, and more comfortable with others knowing about their sexuality) than youths who transited to a gay/lesbian identity and youths who consistently identified as bisexual. Contrary to the hypothesis that females are more sexually fluid than males, female youths were less likely to change identities than male youths. The finding that youths who transited to a gay/lesbian identity differed from consistently gay/lesbian youths suggests that identity integration continues after the adoption of a gay/lesbian sexual identity.