I see quite a few gay men I know settling down with their partners in marriage or civil ceremonies, and then behaving exactly like their heterosexual equivalents and embarking on other relationships often of a short one night stand nature. One Aussie of my acquaintance was married this week, but is still planning to hook up when he travels for work, which is how I met him. He has been with his partner for 17 years. Another man I met was fathering a child through a surrogate with his husband, but was still very happy to have a mutual blow job with me.
The Calvin Coolidge Effect is well studied in many species. This is whereby males exhibit renewed sexual interest if introduced to new receptive sexual partners, even after cessation of sex with prior but still available sexual partners. This effect can be attributed to an increase in sexual responsiveness, and a decrease in the refractory period. The evolutionary benefit to this phenomenon is that a male can fertilize multiple partners.The male may be reinvigorated repeatedly for successful insemination of multiple partners. Many bi and straight men attribute their waning marital sex lives as the trigger to infidelity.