My first major chastity experience was with a couple who were kink friends. She was the Top, he was the (bi) bottom, and I was more of a switch at the time. Long term chastity tends to make me more bottomy and bi, so this worked for us well.
I wasn't allowed to orgasm while with them. I was locked when at home, and mostly with them as well. Occasionally I would get unlocked for an evening, during which both partners used my unlocked parts. He enjoyed the "forced bi oral" aspect, despite being quite bi in general.
I loved that it provided a boundary: since they were married, he remained the bottom while I was the one sexually restricted in terms of use and pleasure/orgasm. Unfortunately, our arrangement ended when they split up; it turned out he leaned more toward the gay side of bisexuality, and their sexual encounters only happened when I was there to "encourage" him.
It lasted a good few years and was a valuable experience. Oddly, I met my current keyholder through them, and we have been best friends for over 10 years now! Our chastity play only started about 3 years ago when we began exploring me serving her.
Chastity works really well with a poly-ish, three-way dynamic as it creates clear boundaries and is just plain hot. It's especially good if you are comfortable being around another guy, and works very well if one or both have a forced bi fetish. It can also work if both partners are Tops; in that case, you avoid typical relationship issues confusing the serving/chastity/bottoming aspects of the slave dynamic. The couple maintains their own relationship, allowing you to remain focused on your role.